Theoretical infrared spectra of some model polycyclic aromatic hydrocarbons: effect of ionization

In order to test the hypothesis of ionized polycyclic aromatic hydrocarbons (PAHs) as possible carriers of the UIR bands, we realized a computational exploration on selected PAHs of small dimension in order to identify which changes ionization would induce on their IR spectra. In this study we performed ab initio calculations of the spectra of neutral and positively ionized naphthalene, anthracene, and pyrene. The results are significantly important. The frequencies in the cations are slightly shifted with respect to the neutral species, but no general conclusion can be reached from the three molecules considered. By contrast, the relative intensities of most vibrations are strongly affected by ionization, leading to a much better agreement between the calculated CH/CC vibration intensity ratios and those deduced from observations.     

Changes of anisotropy of the magnetic susceptibility of rocks induced by a magnetic field

Summary The changes of the anisotropy of magnetic susceptibility of igneous rocks, induced by a magnetic field, are studied. It is proved that changes in the degree of anisotropy of susceptibility and of the orientation of the susceptibility ellispoid of specimens occur due to the configuration of the domain structure under the effect of the magnetic field. The influence of this effect on the total anisotropy of rocks depends on the degree of anisotropy due to the shape factor and on the stability of the domain structure. A model concept is presented, explaining the qualitatively different pattern of the changes of the anisotropy of susceptibility under the effect of the magnetic field in various directions of the specimens.     

Pauling bond strength, bond length and electron density distribution

The power law regression equation, <R(M–O)> = 1.46(<ρ(r _c)>/r)^?0.19, relating the average experimental bond lengths, <R(M–O)>, to the average accumulation of the electron density at the bond critical point, <ρ(r _c)>, between bonded pairs of metal and oxygen atoms (r is the row number of the M atom), determined at ambient conditions for oxide crystals, is similar to the regression equation R(M–O) = 1.41(ρ(r _c)/r)^?0.21 determined for three perovskite crystals at pressures as high as 80 GPa. The pair are also comparable with the equation <R(M–O)> = 1.43(<s>/r)^?0.21 determined for oxide crystals at ambient conditions and <R(M–O)> = 1.39(<s>/r)^?0.22 determined for geometry-optimized hydroxyacid molecules that relate the geometry-optimized bond lengths to the average Pauling bond strength, <s>, for the M–O bonded interactions. On the basis of the correspondence between the equations relating <ρ(r _c)> and <s> with bond length, it seems plausible that the Pauling bond strength might serve a rough estimate of the accumulation of the electron density between M–O bonded pairs of atoms. Similar expressions, relating bond length and bond strength hold for fluoride, nitride and sulfide molecules and crystals. The similarity of the expressions for the crystals and molecules is compelling evidence that molecular and crystalline M–O bonded interactions are intrinsically related. The value of <ρ(r _c)> = r[(1.41)/<R(M–O)>]^4.76 determined for the average bond length for a given coordination polyhedron closely matches the Pauling’s electrostatic bond strength reaching each the coordinating anions of the coordinated polyhedron. Despite the relative simplicity of the expression, it appears to be more general in its application in that it holds for the bulk of the M–O bonded pairs of atoms of the periodic table.     

An environmental assessment of the Charleston Ocean Dredged Material Disposal Site and surrounding areas after partial completion of the Charleston Harbor Deepening Project

A project to deepen shipping and entrance channels in Charleston Harbor was conducted from 1999 to 2002. This generated approximately 22 million cubic yards of sediment for offshore disposal. Assessments of biological and physical conditions in the Charleston Ocean Dredged Material Disposal Site and surrounding areas were conducted prior to deepening (1993-94), and partway through the disposal period (2000). Results from the 2000 survey are presented and compared to the baseline survey. The study area was composed of the disposal zone and surrounding areas and divided into 20 one square mile strata. Within each stratum, benthic grab samples were collected from ten random sites for analysis of sediment composition and contaminants and macrobenthic assemblages. No contaminant levels were above effects range low levels. Results revealed that sediments in the western strata had significantly higher silt/clay content in the 2000 survey when compared to baseline sediments, while sediments east of the disposal zone were similar to baseline. Analyses were performed on a subset of the benthic data that compared baseline to 2000 conditions in western and eastern strata. The benthic communities in western strata were altered following disposal operations. The benthic community east of the disposal area was not different from baseline conditions. These alterations in the benthic community were attributed to changes in bottom habitat characteristics rather than pollution effects.     

Leaching capabilities of iodine monochloride (ICl) and diethylenetriamine pentaacetic acid (DPTA) at different concentrations and pH for some major and trace metals from coal and coal fly ash

In the present study, coal from Chakwal (Pakistan) was leached with an aqueous solutions of iodine monochloride (ICl) and diethylenetriamine pentaacetic acid (DPTA) of different concentrations. The effect of stirring time, concentration and pH was studied on the leaching of different metals from coal. The physicochemical parameters indicated that the coal was of reasonably good quality. The results indicated that with increase in time duration, the extraction of metals increased. In most of the cases, metal concentration increased in the leachate with increasing the concentration of the leaching agents. DPTA was found to be the best leaching agent for most of the metals. Higher extraction of metals from coal fly ash indicated that coal organic matter has a pronounced effect on the leaching. Higher concentration of metals was extracted from virgin coal and coal fly ash at low pH (p?>?0.00) as compared to high pH. DPTA extracted metals in higher concentration from virgin coal and coal fly ash at low pH as compared to ICl. Based on the present study, the most leached metals were Fe, Cu, Mn and the least were Pb, Ni, Cd and Cr.     

Environmental conditions and biological community of the Penzhina and Talovka hypertidal estuary (northwest Kamchatka) in the ice-free season

New data on the abiotic conditions; species composition; abundance, distribution, and migrations of fauna; and feeding interactions in an estuary ecosystem were obtained during expeditions in the mouths of Penzhina and Talovka rivers (northwest Kamchatka). It is revealed that in the ice-free season, the hydrological regime of the estuary is determined by seasonal fluctuations of river runoff, as well as fortnightly and daily variation of tides. The estuary is characterized by hypertidal fluctuations (up to 10–12 m); strong reverse flows (up to 1.0–1.5 m/s), considerable tidal variations in salinity (from 0 to 6–9‰ at the river boundary and from 6–8 to 14–16‰ at the offshore boundary), and high water turbidity (up to 1 000 NTU or more). Based on the spatial structure of the community, three ecological zones with mobile boundaries are distinguished: freshwater (salinity 0–0.1‰), estuarine (0–12.3‰), and neritic (11.2–18.9‰). High turbidity prevents the development of phytoplankton in the estuarine zone (EZ), and the local benthic community is significantly depleted due to the desalination and wide spread of aleuritic silts. Neritic copepods and nektobenthic brackish- water crustaceans generate the maximum abundance and biomass here. The species that have adapted to the local extreme hydrologic conditions dominate and form the basis of the estuarine food chain. Dominant among the EZ vertebrates are such groups as anadromous fishes (smelts, pacific salmons, charrs, and sticklebacks); waterfowl (terns, kittiwakes, cormorants, fulmars, puffins, guillemots, auklets, and wadepipers); and predatory marine mammals (larga, ringed seal, bearded seal, and white whale). The total abundance and biomass of these animals are much higher in the pelagic EZ in comparison to neighboring zones.