Phytoplankton diversity and chlorophyll-A in a polluted estuary

The quantity of phytoplankton in Newark Bay, New Jersey as indicated by chlorophyll-a content of the water, is low in the winter and early spring, and fluctuates greatly during the spring and summer. Chlorophyll-a concentrations are generally less than 20 μg/l until April. Between April and August, three phytoplankton blooms were indicated by chlorophyll-a concentrations as high as 81.4 μg/l. Net phytoplankton diversity values indicated generally eutrophic conditions; however, there was no significant correlation between diversity and chlorophyll-a concentrations. A role of nannoplankton in blooms is indicated.     

Models of travel demand with endogenous preference change and heterogeneous agents

In the literatures of regional science, urban economics, and urban development planning, a working assumption is that individuals respond to incentives and regulations, given their preferences. Models for planning and policy analyses are used to consider what might occur if the incentives or regulations were different. In these models, however, preferences are usually assumed to be given and stable, and agents are usually assumed to be homogeneous. This paper focuses on the implications of making preferences in models of policy implementation endogenously determined and time varying heterogeneous agents. We consider first the recent literature on intertemporal choice and preference change, which cuts across many disciplines, and more briefly the literature on norm-regarding behavior. We then elaborate a simple model of transportation demand—from a static to a dynamic orientation, from fixed and exogenously given preferences of strictly self-regarding agents to endogenously determined and policy-induced preferences of heterogeneous agents—and illustrate its characteristics with simple numerical examples.     

PGE distribution in deformed lherzolites of the Udachnaya kimberlite pipe (Yakutia)

The results of the first study of the PGE distribution in deformed lherzolites of the Udachnaya kimberlite pipe (Yakutia) are presented here. The complex character of evolution of the PGE composition in the Deformed lherzolites is assumed to be the result of silicate metasomatism. At the first stage, growth in the amount of clinopyroxene and garnet in the rock is accompanied by a decrease in the concentration of the compatible PGE (Os, Ir). During the final stage, the rock is enriched with incompatible PGE (Pt, Pd) and Re possible due to precipitation of submicron-sized particles of sulfides in the interstitial space of these mantle rocks.     

The solubility of quartz in aqueous sodium chloride solution at 350°C and 180 to 500 bars

The solubility of quartz in 2, 3, and 4 molal NaCl was measured at 350°C and pressures ranging from 180 to 500 bars. The molal solubility in each of the salt solutions is greater than that in pure water throughout the measured pressure range, with the ratio of solubility in NaCl solution to solubility in pure water decreasing as pressure is increased. The measured solubilities are significantly higher than solubilities calculated using a simple model in which the water activity in NaCl solutions decreases either in proportion to decreasing vapor pressure of the solution as salinity is increased or in proportion to decreasing mole fraction of water in the solvent.     

H 187 - At the Onset of a New Eclipse

CCD photometry data of the T Tauri star H 187 are presented. They show that a new eclipse of this star began at the end of 2004. Since only one eclipse of this star has been observed previously with a duration of 3.5 years, our data indicate that the eclipses of this object are periodic with a period P=4.9 years between eclipses. Thus, in terms of the absolute duration of the eclipses and in terms of their relative length as a fraction of the period, H 187 is one of the most exotic objects in the sky. __________ Translated from Astrofizika, Vol. 48, No. 4, pp. 529–534 (November 2005).     

Application of saddlepoint approximation in reliability analysis of dynamic systems

The application of the saddlepoint approximation to reliability analysis of dynamic systems is investigated. The failure event in reliability problems is formulated as the exceedance of a single performance variable over a prescribed threshold level. The saddlepoint approximation technique provides a choice to estimate the cumulative distribution function (CDF) of the performance variable. The failure probability is obtained as the value of the complement CDF at a specif ied threshold. The method requires computing the saddlepoint from a simple algebraic equation that depends on the cumulant generating function (CGF) of the performance variable. A method for calculating the saddlepoint using random samples of the performance variable is presented. The applicable region of the saddlepoint approximation is discussed in detail. A 10-story shear building model with white noise excitation illustrates the accuracy and effi ciency of the proposed methodology.     

Lateral continuity of basement seismic reflections in 15 Ma ultrafast-spreading crust at ODP Site 1256

The Ocean Drilling Program (ODP) initiated drilling at Site 1256D in the Guatemala Basin, about 1,000 km off the East Pacific Rise to penetrate plutonic rocks, anticipated to be relatively shallow in this region, formed at an ultra-fast spreading rate. IODP Expedition E312 successfully drilled into gabbros at ~1,150 m in basement. Multi-channel seismic traces show weak laterally coherent sub-basement reflections at borehole depths. Synthetic reflectivity seismograms were computed using a Ricker wavelet and impedance profiles from borehole sonic logs. These seismograms show significant sub-basement amplitude peaks. A zero-offset vertical seismic profile, shot on E312, was processed to investigate the authenticity of these reflections and their relationship to borehole geology. A dual scheme of the median filtering and F–K dip filtering was used. Tests with synthetic seismograms indicate the approach is effective at reasonable SNR levels. Downgoing energy is clearly identified but negligible upgoing energy is visible over random noise. These results indicate that lava flows and igneous contacts in upper ocean crust have significant topography on lateral scales less than the Fresnel Zone (~300 m) due to igneous and tectonic processes.     

In situ Raman observation of the crystallization in NaNO3–Na2SO4–H2O solution droplets

Several double salts have been detected in building materials and most of these salts are incongruently soluble compounds. In contrast to single salts, however, no systematic investigations of the crystallization behavior and deleterious effects of incongruently soluble double salts exist. To assess the damage potential of these salts, a systematic investigation of their highly complex behavior is desirable. This paper deals with the crystallization behavior of various solids in the ternary mixed NaNO₃–Na₂SO₄ system including the formation of the double salt darapskite, Na₃NO₃SO₄·H₂O. The crystallization sequence during droplet evaporation experiments at room conditions was determined using Raman and polarization microscopy. The basic idea of this research is to use deviations of the crystallization sequence of a salt or a mixed salt solution from the equilibrium pathway as an indicator to detect the degree of supersaturation. The observed crystallization pathway includes the formation of the metastable phases Na₂SO₄(III), Na₂SO₄(V) and darapskite. The experimental observations are discussed on the basis of the NaNO₃–Na₂SO₄–H₂O phase diagram and the results provide evidence for crystal growth from highly supersaturated solutions in both systems. If the crystals growing under these conditions are confined, these supersaturations result in substantial crystallization pressures.     

An Analytical Model For Threshold Crossing Rates Of Concentration Fluctuations In Dispersing Plumes

A simple analytical model is developed for the meanupcrossing rate of plume concentration fluctuations assuming that thisprocess can be well approximated by a lognormal process. The resultingexpression requires only the specification of the in-plume fluctuationintensity and in-plume Taylor micro-time scale and, hence, does notexplicitly involve the joint probability density function of theconcentration and its derivative. The analytical model provides agood fit to some field measurements of the mean upcrossing rate ina dispersing plume.