Putting Hydrogeologic Site Studies on Track     

Harry E. LeGrand  Lars Rosen 《Ground water》1998,36(2):193-193

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Observations of energetic ions in inverted V events     

Bengt Hultqvist  Hans Borg 《Planetary and Space Science》1978,26(7):673-689

Simultaneous measurements of keV ions and electrons with the ESRO 1A satellite have shown the following ion characteristics among others. Ions of about 6 keV energy are strongly field-aligned on the flanks of the inverted V events (mainly through the disappearance of the ion flux near 90° pitch angle). Field-aligned electron fluxes are often found in the same regions of the inverted V events where the ions are field-aligned. At the centre of inverted V events isotropization occurs (except in some small events). The 1 keV ion flux at large pitch angles (80°) is generally not reduced very much when the 6 keV, 80° ion flux shows strongly decreased values. The ratio of the 1 to 6 keV ion flux has a maximum near the centre of an inverted V event where the electron spectrum is hardest and the 6 keV ions are isotropic (or nearly isotropic).The observations are interpreted in terms of a model with two oppositely directed field-aligned electrostatic potential drops: one upper accelerating electrons downward and one lower, produced by the electron influx, which accelerates ions downward. Ion scattering in turbulent wave fields is proposed to be responsible for the observation that the 1 keV ion flux at large pitch angles does not decrease strongly where the 6 keV ion flux does and as an explanation of the isotropization at the centre of the event. The source problem for the ions is eliminated by the precipitating electrons ionizing continuously the thin neutral atmosphere even at altitudes of a few thousand kilometers.  相似文献   

Dissociation of hydrogen sulphide in seawater and comparison of pH scales     

Tom Almgren  David Dyrssen  Bengt Elgquist  Olof Johansson 《Marine Chemistry》1976,4(3):289-297

The protonization constant of HS^? (K₁₂) has been determined potentiometrically (glass electrode) at atmospheric pressure in synthetic seawater in the salinity range 2.5–40‰ at 5 and 25°C and in NaCl solutions in the formal ionic strength of 0.1–0.8 M at 5 and 25°C. The difference between synthetic seawater and an NaCl solution with the same formal ionic strength can be explained in terms of the complexation of H⁺ by sulphate in seawater. These results can be used to compare the pH scales suggested by Hansson (1973c) and Bates (1975). Furthermore, comparison between the present values of K₁₂ and those of Goldhaber and Kaplan (1975) makes it possible to compare the conventional pH scale with Hansson's titration pH scale. The conditional protonization constant of HS^? in seawater of different salinities can be used to modify the Gran plots (Hansson and Jagner, 1973) for alkalinity measurements in anoxic seawater. Ion-pair formation between HS^? and Mg²⁺ or Ca²⁺ seems to be very weak.  相似文献   

Stability of the calcium sulphate ion pair at the ionic strength of seawater by potentiometry     

Bengt Elgquist  Margareta Wedborg 《Marine Chemistry》1979,7(4):273-280

The stability of the ion pair CaSO₄ was determined from measurement of the change in calcium ion activity with medium composition at constant ionic strength. A calcium selective PVC-matrix liquid membrane electrode was used to monitor the calcium ion activity. All measurements were performed at 1 atm, 25 ± 0.1°C and 0.7 M formal ionic strength. The evaluation of the stability constant depends on the degree of complexation between calcium and chloride and between sodium and sulphate. The dependence of K_CaSO4, on K_NaSO4 and K_CaCl can be described by the following relations:K_CaSO4=17.7 K_CaCl+16.5 (K_NaSO4=1.8)K_CaSO4=18.8 K_CaCl+17.3 (K_NaSO4=2) for K_CaCl=0–1A value of K_CaSO4=25.4 is suggested.  相似文献   

Current status of mobile and static sampling gears used in resource surveys     

Reid  David G.; Annala  John; Rosen  Shale; Pol  Mike; Cadrin  Steve X.; Walsh  Stephen J. 《ICES Journal of Marine Science》2007,64(8):1607-1609

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Application of multivariate geostatistics in the investigation of heavy metal contamination of roadside dusts from selected highways of the Greater Toronto Area, Canada     

Y. Nazzal  Habes Ghrefat  Marc A. Rosen 《Environmental Earth Sciences》2014,71(3):1409-1419

A good understanding of roadside soil contamination and the location of pollution sources is important for addressing many environmental problems. The results are reported here of an analysis of the content of metals in roadside dust samples of four major highways in the Greater Toronto area (GTA) in Ontario, Canada. The metals analyzed are Pb, Zn, Cd, Ni, Cr, Cu, Mn, and Fe. Multivariate geostatistical analysis [correlation analysis (CA), principal component analysis (PCA), and hierarchical cluster analysis (HCA)] were used to estimate soil chemical content variability. The correlation coefficient shows a positive correlation between Cr–Cd, Mn–Fe, and Fe–Cu, while negatively between Zn–Cd, Mn–Cd, Zn-Cr, Pb–Zn, and Ni–Zn. PCA shows that the three eigenvalues are less than one, and suggests that the contamination sources are processing industries and traffic. HCA classifies heavy metals in two major groups. The cluster has two larger subgroups: the first contains only the variables Fe, Mn, Cu, Cr, Ni, and Pb, and the second includes Cd and Zn. The geostatistical analysis allows geological and anthropogenic causes of variations in the contents of roadside dust heavy metals to be separated and common pollution sources to be identified. The study shows that the high concentration of traffic flows, the parent material mineralogical and chemical composition, and land use are the main sources for the heavy metal concentration in the analyzed samples.  相似文献   

Hydrodynamic simulations of molecular outflows driven by slow-precessing protostellar jets     

Michael D. Smith  Alexander Rosen 《Monthly notices of the Royal Astronomical Society》2005,357(2):579-589

We present hydrodynamic simulations of molecular outflows driven by jets with a long period of precession, motivated by observations of arc-like features and S-symmetry in outflows associated with young stars. We simulate images of not only H₂ vibrational and CO rotational emission lines, but also of atomic emission. The density cross-section displays a jaw-like cavity, independent of precession rate. In molecular hydrogen, however, we find ordered chains of bow shocks and meandering streamers which contrast with the chaotic structure produced by jets in rapid precession. A feature particularly dominant in atomic emission is a stagnant point in the flow that remains near the inlet and alters shape and brightness as the jet skims by. Under the present conditions, slow jet precession yields a relatively high fraction of mass accelerated to high speeds, as also attested to in simulated CO line profiles. Many outflow structures, characterized by HH 222 (continuous ribbon), HH 240 (asymmetric chains of bow shocks) and RNO 43N (protruding cavities), are probably related to the slow-precession model.  相似文献   

Hydrodynamical Simulations of Molecular Dynamics in Supersonic Turbulent Flow     

Georgi Pavlovski  Michael D. Smith  Mordecai–Mark Mac Low  Alexander Rosen 《Astrophysics and Space Science》2004,292(1-4):69-75

Here we present results from simulations of turbulence in star forming environments obtained by coupling three-dimensional hydrodynamical models with appropriate chemical processes. We investigate regimes of decaying high-speed molecular turbulence. Here we analyse PDFs of density for the volume, mass, molecular mass and the energy distribution over the range of scales. We compare our results to those previously obtained for isothermal turbulence and suggest possible explanations.  相似文献   

Simulations of evolving or outbursting molecular protostellar jets     

Alexander Rosen  Michael D. Smith 《Monthly notices of the Royal Astronomical Society》2003,343(1):181-191

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α-process Elements in the Galaxy: A Possible GAIA Contribution     

Gražina Tautvaišienė  Bengt Edvardsson 《Astrophysics and Space Science》2002,280(1-2):143-150

The sensitivity of stellar spectra to α/Fe abundance changes is investigated with the aim to be detected photometrically and employed for the scientific goals of the GAIA mission. A grid of plane parallel, line blanketed, flux constant, LTE model atmospheres with different [α/Fe] ratios was calculated. As a first step, the modeled stellar energy fluxes for solar-type stars and giants were computed and intercompared. The spectral sensitivity to α/Fe abundance changes is noticeable and has to be taken into account when selecting photometric filters for GAIA. The Ca II H and K lines and Mg I b triplet are the most sensitive direct indicators ofα/Fe abundance changes. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献