排序方式： 共有63条查询结果，搜索用时 46 毫秒
41.
Azra Bozcaarmutlu Canan Sapmaz Zuleyha Aygun Emel Arinç 《Marine environmental research》2009,67(4-5):167-176
Aim of this study was to determine the extent of pollution in the West Black Sea Coast of Turkey by measuring CYP1A associated EROD activity, phase II enzyme, glutathione S-transferase and antioxidant enzymes, catalase and glutathione reductase activities and immunochemical detection of CYP1A protein level in the liver of mullet. The fish samples were caught from six locations having a varying degree of pollution in the West Black Sea Region of Turkey in August 2005, 2006 and 2007. Mullets caught from Zonguldak Harbour, Ere?li Harbour and Gülüç Stream’s Mouth displayed 6–9-fold higher EROD, 2–4-fold higher glutathione S-transferase and 2–3-fold higher catalase activities than the reference site, Amasra. Total polyaromatic hydrocarbon levels in mullets caught from these locations were also significantly higher (2–4-fold) than Amasra. The results of this study indicate that Zonguldak Harbour, Ere?li Harbour and Gülüç Stream are highly polluted by polycyclic aromatic hydrocarbons and related contaminants. 相似文献
42.
V. V. Emel’yanenko 《Solar System Research》2017,51(1):59-63
As follows from dynamical studies, in the course of evolution, most near-Earth objects reach orbits with small perihelion distances. Changes of the asteroids in the vicinity of the Sun should play a key role in forming the physical properties, size distribution, and dynamical features of the near-Earth objects. Only seven of the discovered asteroids are currently moving along orbits with perihelion distances q < 0.1 AU. However, due to the Kozai–Lidov secular perturbations, the asteroids, having recently passed near the Sun, could by now have moved to orbits farther from the Sun. In this study, we found asteroids that have been recently orbiting with perihelion distances q < 0.1 AU. Asteroids may be on such orbits for hundreds to tens of thousands of years. To carry out astrophysical observations of such objects is a high priority. 相似文献
43.
Solar System Research - New data on the distribution of distant trans-Neptunian objects and on the properties of comets indicate the importance of dynamical processes in the outer part of the... 相似文献
44.
This paper analyzes the distribution of the orbits of near-Earth minor bodies from the data on more than 7500 objects. The
distribution of large near-Earth objects (NEOs) with absolute magnitudes of H < 18 is generally consistent with the earlier predictions (Bottke et al., 2002; Stuart, 2003), although we have revealed
a previously undetected maximum in the distribution of perihelion distances q near q = 0.5 AU. The study of the orbital distribution for the entire sample of all detected objects has found new significant features.
In particular, the distribution of perihelion longitudes seriously deviates from a homogeneous pattern; its variations are
roughly 40% of its mean value. These deviations cannot be stochastic, which is confirmed by the Kolmogorov-Smirnov test with
a more than 0.9999 probability. These features can be explained by the dynamic behavior of the minor bodies related to secular
resonances with Jupiter. For the objects with H < 18, the variations in the perihelion longitude distribution are not so apparent. By extrapolating the orbital characteristics
of the NEOs with H < 18, we have obtained longitudinal, latitudinal, and radial distributions of potentially hazardous objects in a heliocentric
ecliptic coordinate frame. The differences in the orbital distributions of objects of different size appear not to be a consequence
of observational selection, but could indicate different sources of the NEOs. 相似文献
45.
N. Yu. Emel’yanenko 《Solar System Research》2012,46(3):181-194
This paper studies the dynamical evolution of 97 Jupiter-family comets over an 800-year time period. More than two hundred encounters with Jupiter are investigated, with the observed comets moving during a certain period of time in an elliptic jovicentric orbit. In most cases this is an ordinary temporary satellite capture of a comet in Everhart??s sense, not associated with a transition of the small body into Jupiter??s family of satellites. The phenomenon occurs outside the Hill sphere with comets with a high Tisserand constant relative to Jupiter; the comets?? orbits have a small inclination to the ecliptic plane. An analysis of 236 encounters has allowed the determination within the planar pair two-body problem of a region of orbits in the plane (a, e) whose semimajor axes and eccentricities contribute to the phenomenon under study. Comets with orbits belonging to this region experience a temporary satellite capture during some of their encounters; the jovicentric distance function has several minima; and the encounters are characterized by reversions of the line of apsides and some others features of their combination that are intrinsic to comets in this region. Therefore, this region is called a region of comets with specific features in their encounters with Jupiter. Twenty encounters (out of 236), whereby the comet enters an elliptic jovicentric orbit in the Hill sphere, are identified and investigated. The size and shape of the elliptic heliocentric orbits enabling this transition are determined. It is found that in 11 encounters the motion of small bodies in the Hill sphere has features the most important of which is multiple minima of the jovicentric distance function. The study of these 20 encounters has allowed the introduction of the concept of temporary gravitational capture of a small body into the Hill sphere. An analysis of variations in the Tisserand constant in these (20) encounters of the observable comets shows that their motion is unstable in Hill??s sense. 相似文献
46.
N. Emel Ganapati 《Natural Hazards》2013,65(3):1783-1799
Despite a growing literature on post-disaster recovery, our understanding of how housing recovery is measured remains limited. This paper is a step in filling the gap in the literature by presenting an overview of how recovery organizations measured post-disaster permanent housing recovery in Gölcük, Turkey, following the August 17, 1999 earthquake. Based on in-depth interviews, focus groups, participant observation, and review of secondary sources, the paper highlights the limitations of measuring housing recovery as the number of permanent housing units built in a timely manner. It suggests that recovery organizations need to measure post-disaster housing recovery by developing context-specific, process- and outcome-oriented measures. In the case of Gölcük, process-oriented measures could have been related to the land appropriation, public participation processes, and inter-organizational collaboration while outcome-oriented measures could have been related to the level of satisfaction with homes built and equity among the housing beneficiaries. 相似文献
47.
Emel’yanov N. V. Arlot J.-E. Hestroffer D. Varfolomeev M. I. Beskakotov A. S. 《Solar System Research》2022,56(5):308-317
Solar System Research - The article presents new results on motion modeling and creation of ephemeris of satellites of asteroids based on observations. In previous work on the project, ephemeris of... 相似文献
48.
E. P. Lelikov I. B. Tsoy N. K. Vagina T. A. Emel’yanova E. P. Terekhov V. D. Khudik 《Russian Journal of Pacific Geology》2011,5(5):387-399
This paper reports the composition and age of rocks dredged from the Kashevarov Trough (central Sea of Okhotsk) during cruise
41 of the R/V Akademik M.A. Lavrentyev in 2006. It was found that the Late Cretaceous and Eocene volcanics from the Kashevarov Trough and Okhotsk-Chukotka volcanic
belt, structures of which are traceable in the Sea of Okhotsk, have similar petrographic and geochemical features. The Cenozoic
sedimentary cover consists of three different-age complexes: (1) the late Oligocene (∼28.2–24.0 Ma); (2) the terminal late
Oligocene-early Miocene (24.0–20.3 Ma); (3) the terminal late Pliocene-early Pleistocene (2.0–1.0 Ma). The upper Oligocene-lower
Miocene sediments were deposited in relatively shallow-water settings, whereas the late Pliocene-early Pleistocene complex
was formed in deeper environments, which was probably determined by tectonic processes. The geological data indicate that
the Kashevarov Trough and the surrounding underwater rises represented in the Oligocene-early Miocene a single shelf zone
of the Sea of Okhotsk, which is underlain by a structurally integral Mesozoic basement and is now subsided to depths of 800–1000
m. 相似文献
49.
Grain size and mineral composition of core sediments were used to investigate influences of various terrestrial and marine conditions, which have prevailed on the southwestern Black Sea shelf during the Holocene. Siliciclastic mud with small amounts of sand and gravel from nearby coastal hinterland is the principal sediment type, whereas sediments deposited near the shelf edge and the Istanbul Strait and off the Duru Lake （a paleo-river mouth） constitued large quantities of sand and gravel of both biogenic and terrigenic origin. Variable amounts of aragonite, 1 nmmicas, quartz, feldspars, calcite and dolomite constitute the dominant non-clay minerals in bulk sediments. The clay mineral assemblage in the 〈 2 μm fraction is made up of smectite, illite, kaolinite and chlorite. Aragonite and calcite are mainly derived from benthic accumulations, whereas feldspars （mainly plagioclase） and smectite reflect magmaticvolcanic provenance and the distribution of 1 nm-micas and chlorite correlate with nearby metamorphic sources onland. Nevertheless, grain size and mineral distribution generally indicate a combination of effects of wind and wave climate, longshore and offshore cyclonic currents, changing sea-level stands and nearby source rock and morphological conditions. It is also suggested that at least part of clay minerals could be derived from the northwesterly Danube River input. 相似文献
50.
V.V. Emel’yanenko 《Earth, Moon, and Planets》2005,97(3-4):341-351
The origin of Jupiter-family comets is linked to the intermediate stage of evolution through the Centaur region. Thus the structure of the Centaur population provides important constraints on sources of short-period comets. We show that our model of the Oort cloud evolution gives results which are consistent with the orbital distribution of observed Centaurs. In particular, it explains the existence of the large population of Centaurs with semimajor axes greater than 60 AU. The main source for these objects is the inner Oort cloud. Both Jupiter-family and Halley-type comets are produced by Centaurs originating from the Oort cloud. The injection rate for Jupiter-family comets coming from the inner Oort cloud is, at least, not less than that for a model based on the observed sample of high-eccentricity trans-Neptunian objects. 相似文献