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191.
Andrzej Kaim Alexander Nützel Hugo Bucher Thomas Brühwiler Nicolas Goudemand 《Swiss Journal of Geoscience》2010,103(1):121-128
An Early Triassic (Griesbachian) gastropod fauna is reported from South China (Shanggan, Guangxi) and consists of four species:
Bellerophon abrekensis, Wannerispira
shangganensis Kaim & Nützel sp. nov., Naticopsis sp., and Palaeonarica
guangxinensis Kaim & Nützel sp. nov. The taxon Wannerispira Kaim & Nützel nom. nov. replaces Pagodina Wanner non Van Beneden. This is the first report of Bellerophon abrekensis from China. Previously, it was only known from its type locality in Far East Russia. Wannerispira
shangganensis sp. is the first certain Triassic report of the Permian subfamily Neilsoniinae and represents a holdover taxon. The neritimorph
Palaeonarica is reported for the first time from the Early Triassic and this is the oldest occurrence of this genus. Compared with other
Griesbachian gastropods, the present material is relatively well preserved so that the taxonomy rests on rather firm ground.
Very few nominal taxa have been reported from the Griesbachian and therefore the present report presents substantial additional
information about gastropods from the aftermath of the end-Permian mass extinction event. The gastropod association from Shanggan
shares one species with Primorye, Far East Russia (B. abrekensis). Two species, W. shangganensis and P. guangxinensis, closely resemble specimens reported from the Griesbachian of Oman. This could suggest that Griesbachian gastropod faunas
of the Tethys were rather homogenous although the data are still scarce. 相似文献
192.
The scope of this study is to evaluate the parameters of the gypsum–anhydrite strata karstification under the influence of
the quarry exploitation of Jaziv sulphur field (West Ukraine) accompanying by drainage. The quarry drainage provoked the enormous
depression cone forming with 100 km2 in area and the corresponding intensification of chemical denudation of the gypsum–anhydrite strata. The gypsum karstification
rate for the 29-year period of the quarry drainage was 0.06% with the dissolved rock volume of 1,328,507 m3 that is about 80 times higher than in natural conditions. For the drainage period (29 years) the karst denudation rate was
17,952 m3/km2 against the natural background of 231.3 m3/km2. The absolute value of artificial denudation for the studied massif area is 1.79 cm for 29 years or 0.062 mm/year while the
denudation rate under natural conditions would be 0.231 cm for 29 years or 0.0008 mm/year. The forecasted volumes of the surface-evident
collapses are evaluated using the relationship between the calculated amount of dissolved sulphate rocks and volumes of the
current surface-evident collapses. According to this evaluation, the current collapses correspond to about 34% only from the
dissolved rocks volume calculated for the drainage period. 相似文献
193.
RAT0455+1305 was discovered during the Rapid Temporal Survey which aims in finding any variability on timescales of a few minutes to several hours. The star was found to be another sdBV star with one high amplitude mode and relatively long period. These features along with estimation of T eff and log?g makes this star very similar to Balloon?090100001. Encouraged by prominent results obtained for the latter star we have decided to perform white light photometry on RAT0455+1305. In 2009 we used the 1.5 m telescope located in San Pedro Martir Observatory in Mexico. Fourier analysis confirmed the dominant mode found in the discovery data, uncovered another peak close to the dominant one, and three peaks in the low frequency region. This shows that RAT0455+1305 is another hybrid sdBV star pulsating in both p- and g-modes. 相似文献
194.
Ranjeev Misra Andrzej A. Zdziarski 《Monthly notices of the Royal Astronomical Society》2008,387(2):915-920
We develop a model of an accretion disc in which the variability induced at a given radius is governed by a damped harmonic oscillator at the corresponding epicyclic frequency. That variability induces both linear and non-linear responses in the locally emitted radiation. The total observed variability of a source is the sum of these contributions over the disc radius weighted by the energy dissipation rate at each radius. It is shown that this simple model, which effectively has only three parameters including the normalization, can explain the range of the power spectra observed from Cyg X-1 in the soft state. Although a degeneracy between the black hole mass and the strength of the damping does not allow a unique determination of the mass, we can still constrain it to ≲(16–20) M⊙ . We also show that our model preserves the observed linear rms–flux relationship even in the presence of the non-linear flux response. 相似文献
195.
A simple incremental model describing the pre-failure behaviour of granular soils is presented. The model describes both the dry/fully drained and undrained response. It takes into account an initial anisotropy of soil and an initial state defined as either contractive or dilative. A physically sound definition of loading/unloading is assumed, which differs from elasto-plastic approaches. The model is based on extensive empirical data and gives predictions conformable with experimental results. It also describes pre-failure instabilities of granular soils, both dry/fully drained and undrained. The Hill’s criterion was used to examine stability. It was shown that this condition can be formulated either in terms of the effective stresses or by the total stresses. In the extreme cases of either dry/fully drained or undrained conditions, these alternative formulations are equivalent. This is not so in the case of partial drainage of pore water and associated volumetric deformations as well as pore pressure changes. The model describes the pre-failure instabilities well, and additionally allows for analytical derivation of the instability line. It was shown that the second order work, appearing in the Hill’s condition, is equivalent to the entropy source. 相似文献
196.
Marek Gołkowski Marek Kubicki Morris Cohen Andrzej Kułak Umran S. Inan 《Acta Geophysica》2011,59(1):183-204
Variations in the global atmospheric electric circuit are investigated using a wide range of globally spaced instruments observing
VLF (∼10 kHz) waves, ELF (∼300 Hz) waves, Schumann resonances (4–60 Hz), and the atmospheric fair weather electric field.
For the ELF/VLF observations, propagation effects are accounted for in a novel approach using established monthly averages
of lightning location provided by the Lightning Image Sensor (LIS) and applying known frequency specific attenuation parameters
for daytime/nighttime ELF/VLF propagation. Schumann resonances are analyzed using decomposition into propagating and standing
waves in the Earth-ionosphere waveguide. Derived lightning activity is compared to existing global lightning detection networks
and fair weather field observations. The results suggest that characteristics of lightning discharges vary by region and may
have diverse effects upon the ionospheric potential. 相似文献
197.
Piotr Lubiski Andrzej A. Zdziarski 《Monthly notices of the Royal Astronomical Society》2001,323(2):L37-L42
We study properties of Fe K lines of a large sample of Seyfert 1s observed by ASCA . Fits with power laws and Gaussian lines yield the average linewidth and equivalent width of 0.22±0.03 keV and 0.13±0.01 keV, respectively. Thus, the typical lines are weak and narrow. We then obtain the average line profile of all our spectra, and find it to consist of a narrow core and blue and red wings, with the red wing being much weaker than that of e.g. MCG −6-30-15. We obtain three average spectra of Seyferts grouped according to the hardness, and find the equivalent width of the core (originating in a remote medium) to be ≃50 eV in all three cases. The wings are well fitted by a broad line from a disc with strong relativistic effects. Its equivalent width correlates with the slope, increasing from ∼70 eV for the hardest spectrum to ∼120 eV for the softest one. The inner disc radius decreases correspondingly from ∼40 to ∼10 gravitational radii, and the fitted disc inclination is ∼45°. The obtained correlation between the slope and the strength of the broad Fe K line is found to be consistent with the previously found correlation of the slope and Compton reflection. 相似文献
198.
Fen ecosystem responses to water‐level fluctuations during the early and middle Holocene in central Europe: a case study from Wilczków,Poland 下载免费PDF全文
Mateusz Płóciennik Andrzej Kruk Jacek Forysiak Dominik Pawłowski Kamila Mianowicz Scott Elias Ryszard K. Borówka Marek Kloss Milena Obremska Marek Krąpiec Piotr Kittel Sławomir Żurek 《Boreas: An International Journal of Quaternary Research》2015,44(4):721-740
This paper presents a palaeoenvironmental reconstruction of the Wilczków fen (central Poland). The fen developed in an inactive valley at the onset of the Holocene (~11 ka BP) and peat accumulation lasted until 5.7 ka BP. Multi‐proxy reconstructions were made on the basis of palaeobotanical, cladoceran, chironomid, beetle and geochemical analyses. A Kohonen self‐organizing map (SOM, unsupervised artificial neural network) of the biotic sequence distinguished four stages of fen history. Stage X1 (11.0–10.7 ka BP) was relatively wet and cool. Organic matter started to accumulate but the habitat conditions remained unstable. Moss, sedge and fern communities then developed. Sedimentary changes reveal an intensive groundwater supply at that time. Numerous and diverse chironomid and cladoceran subfossils indicate nearly permanent aquatic conditions. During stage Y1 (10.6–9.2 ka BP) conditions were dry and the upper peat layer desiccated. Cladocera nearly disappeared whereas chironomids were represented by semi‐terrestrial and predatory (Tanypodinae) species. Conditions started to be more reducing. All the remaining samples belonged to the interweaving stages X2 and Y2. Stage Y2 (mostly 9.1–7.3 and 6.0–5.7 ka BP) was also dry but humidity increased towards the top. Oxidizing conditions occurred and the pH became more alkaline, favouring Cladium mariscus. The basin received mostly allochthonous matter input at that time. Stage X2 (mostly 6.8–6.1 ka BP) was humid and warm. The groundwater supply remained low but there was an increase in precipitation, changing local conditions to ombrotrophic. Species‐rich chironomid and cladoceran communities were associated with temporary pools. Finally, conditions returned to those characteristic of stage Y2. The presented reconstruction documents long‐term abiotic and biotic changes determined by water supply, including groundwater outflow, which have rarely been detected at a multi‐proxy scale. We show that inactivated valley fens are sensitive to climate‐driven hydrological fluctuations. Kohonen neural networks appear to be a promising method for analysing variability in multi‐proxy data. 相似文献
199.
200.
Chemometric methods are powerful in finding hidden structures and latent information in environmental and other analytical datasets. This work shows the application of cluster analysis, discriminant analysis, and support vector machines for the evaluation of waterbodies in the Polish Tatra Mountains. After the analysis of in situ parameters and the determination of concentrations of cations and anions, cluster analysis shows that the previous separation into Western Tatras and High Tatras should be reconsidered, as the Bystra stream in the border region might have been incorrectly assigned to the Western Tatras up to now. Discriminant analysis not only confirms the geographical separation of waterbodies, but also the fact that the sampling time is a crucial factor in environmental analysis. Samples taken in different months do not result in a homogenous object of investigation. A uniform date should therefore be chosen so that the results will be comparable. The influence of the sampling month on the classification of samples is also approved by support vector machines. 相似文献