震旦纪地层黄铁矿硫同位素组成时－空变化特征及扬子地块与晚元古超大陆关系的论证

 扬子地区早震旦世时期沉积岩黄铁矿具有重的硫同位素组成,其δ¹⁴S值从早震旦世椿木组地层的24‰左右逐渐变得更正。在早震旦世扬子地区广泛沉积碳酸锰矿和黑色页岩的民乐组时期达到极正值+60‰,然后又降低至+16‰-+20‰。上述硫同位素组成的时-空变化特征支持了扬子地块属晚元古Rodinia超大陆的一个组成部分的假设。从晚震旦世早期陡山沱组底部开始,沉积岩中黄铁矿硫同位素的δ¹⁴SS出现负值,并继续降低至-27‰以下。早震旦世晚期-晚震旦世早期沉积岩中硫同位素组成特征反映了沉积盆地古海洋环境的剧烈变化,它与大约7亿年时Rodinia超大陆的解体以及扬子地块与其它大陆分离的地质推测相吻合。     

Long-term improvements in water quality due to sewage abatement in the lower Hudson River

Long-trend trends in dissolved oxygen (DO) and total coliform bacteria concentrations are used to evaluate the impact of almost 60 yr of sewage abatement and treatment in the lower Hudson River near New York City. Although some water pollution control plants have been in operation in the region since the 1930s, the most significant abatement of untreated sewage in the lower Hudson River has occurred since the late 1970s, when most of the existing plants were upgraded to secondary treatment, and additional plants were constructed. From at least 1922 through the early 1960s, average summer DO percent saturation varied between 35% and 50% in surface waters and 25% and 40% in bottom waters. Beginning in the late 1970s, DO concentrations generally increased through the 1980s and especially into the 1990s, coinciding with the upgrading of the 7.4 m³ s^?1 (170 million gallons per day, mgd) North River plant to secondary treatment in the spring of 1991. Average summer percent saturation in the early 1990s exceeded 80% in surface waters and 60% in bottom waters. In addition, summer DO minima have increased from less than 1.5 mg 1^?1 in the early 1970s to greater than 3.0 mg 1^?1 in the 1990s, and the duration of hypoxia during summer months has been reduced. Total coliforms also display strong declining trends from the 1970s into the 1990s, with declines attributed to plant upgrades, construction of two New York City plants (North River and Red Hook) in the mid 1980s, and improved operation of the sewer system.     

Acceleration of multiply charged ions of the anomalous cosmic-ray component at the heliosphere boundary

The formation of the energy spectra of heavy ions at the front of a parallel shock is considered taking into account ionization and recombination during the acceleration. An analytic solution for ions with three possible charge states is obtained and applied to the acceleration of the anomalous cosmic-ray component at the boundary of the heliosphere. In addition, a more general numerical model for such acceleration at a spherical shock front is developed and used to obtain the energy dependence of the mean charges for C, N, O, Ne, Si, S, Ar, and Fe ions. The model implies that highly excited ions begin to dominate over ions with low charges at energies above 1 MeV/nucleon, in agreement with observational data.     

Variations in Stable Carbon Isotopic Composition of n-Alkanes from Ordovician and Triassic-Derived Oils in Lunnan Oilfield, Tarim Basin, NW China： Global Paleoenvironmental Constraints

Molecular stable carbon isotope technique was employed to study well-sourced crude oils collected from a single drilling well and from the entire Lunnan oilfield, Tarim Basin, NW China. The stable carbon isotopic composition of n-alkanes from crude oils showed that Ordovi-clan-derived oils are enriched in ^13C and Triassic-derived oils are depleted in ^13C. This is consistent with the distribution and evolution trend of stable carbon isotope ratios in crude oils/organic matter from all over the world in geological history (Stahl, 1977; Andrusevich et al. ,1998). An extensive survey of literature indicates that, except for thermal maturity, organic matter input and depositional environment, paleoenvironmental background is another key factor that affects the stable carbon isotopic composition of Ordovician- and Triassic-derived crude oils. The results showed that gas chromatographic-isotope ratio mass spectrometry ( GC-C-IRMS), combining with biogeoehemical evolution of organic matter in geological history, may be a powerful tool in refining oil/oil, oil/source correlations in multi-age, multi-source petroliferous basins like Tarim.     

Masses of protostars with methanol protoplanetary disks

The masses of 12 protostars assumed to be the central bodies in circumstellar protoplanetary disks are estimated based on analysis of their methanol maser spectra and fine spatial structure. The calculations are based on the hypothesis that the class II methanol maser lines are formed in an edge-on Keplerian disk, while the thermal methanol emission and CS lines are formed in a cocoon around the protostar. This provides information about the velocities of the protostar and the methanol maser condensations relative to the center. In most of the star-forming regions studied, the derived masses are within limits admissible for disks around massive OB stars. The masses are in good agreement with the calculations of other authors based on models of the velocity gradients of the maser features. It is suggested that the methanol spectra display a triplet structure in which the two lateral features are class II methanol lines and the central component is a class I methanol maser line or thermal methanol line. This is consistent with the fact that the correlation of regions of maser emission with regions of emission of dense molecular gas in the CS line is about twice as strong(about 100%) as the correlation with ultracompact HII regions (about 50%). This should be taken into account when modeling protoplanetary disks and star-forming regions.     

The earthquake of 6 September 2002 and the seismic history of Palermo (Northern Sicily,Italy): Implications for the seismic hazard assessment of the city

On September 6, 2002, a M_L = 5.6 earthquake, occurring some tens of kilometres offshore from the Northern Sicilian coast (Southern Tyrrhenian Sea), slightly damaged the city of Palermo and surroundings (degree 6 in the European Macroseismic Scale 1998). The macroseismic investigation of the shock and a detailed study of effects of the main earthquakes which affected Palermo in the past have been performed in order to evaluate the seismic response of the city. Moreover, the comparison of the recent event, which is instrumentally constrained, with historical earthquakes allows us to infer new insights on the seismogenic sources of the area, that seem located offshore in the Tyrrhenian sea.In the last 500 years, Palermo has never been completely destroyed but has suffered effects estimated between intensities 6 and 8 EMS-98 many times (1693, 1726, 1751, 1823, 1940, 1968, 2002). The damage scenarios of the analysed events have shown that damage distribution is strongly conditioned by soil response in the different parts of the city and by a high building vulnerability, mainly in the historical centre and in the south-eastern zone of the modern city. As a matter of fact, Palermo has always suffered greater effects than those reported for other nearby localities. The hazard assessment obtained using observed site intensities has shown that the probability of occurrence for intensity 8 (the strongest intensity observed in Palermo) exceeds 99% for 550 years, while the estimated mean return period is 152 ± 40 years. These results, in connection with building vulnerability due to the urban expansion before the introduction of seismic code, suggest that the city is exposed to a relatively high seismic risk.This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first 3 months after its submission to Journal of Seismology.     

Radio and optical spectral studies of radio sources

Optical identifications and an analysis of the radio spectra of eight radio sources from a flux-density-complete sample at declinations 4°–6° (B 1950) are presented. The observations were carried out at 4000–9000 Å on the 6-m telescope of the Special Astrophysical Observatory and at 0.97–21.7 GHz on the RATAN-600 telescope. Five of the eight sources are quasars and three are emission-line radio galaxies.     

Observations of stellar objects at a shell boundary in the star-forming complex in the galaxy IC 1613

The single region of ongoing star formation in the galaxy IC 1613 has been observed in order to reveal the nature of compact emission-line objects at the edges of two shells in the complex, identified earlier in Hα line images. The continuum images show these compact objects to be stars. Detailed spectroscopic observations of these stars and the surrounding nebulae were carried out with an MPFS spectrograph mounted on the 6-m telescope of the Special Astrophysical Observatory. The resulting stellar spectra were used to determine the spectral types and luminosity classes of the objects. Of star we identified the only object of this spectral type in IC 1613. The results of optical observations of the multishell complex are compared to 21-cm radio observations. The shells harboring the stars at their boundaries constitute the most active part of the star-forming region. There is evidence that shocks have played an important role in the formation of the shells.     

Thermal emission of methanol and other molecules at millimeter wavelengths

The paper reports the results of a survey of Galactic star-forming regions in the methanol lines 8_?1–7₀ E at 229.8 GHz, 3_?2–4_?1 E at 230.0 GHz, 0₀–1_?1 E at 108.9 GHz, and a series of J ₁–J ₀ E lines near 165 GHz. In addition to the methanol lines, lines of methyl cyanide (CH₃CN), cyanoacetylene (HC₃N), methyl formate (HCOOCH₃), and sulphur dioxide (SO₂) were detected. Analysis of the data indicates that the methanol emission arises in warm (30–50 K) gas.