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81.
Charles-Philippe Lienemann Marc Monnerat Janusz Dominik Didier Perret 《Aquatic Sciences - Research Across Boundaries》1999,61(2):133-149
82.
Joanna Święta-Musznicka Małgorzata Latałowa Józef Szmeja Monika Badura 《Journal of Paleolimnology》2011,45(3):369-383
Large numbers of sub-fossil remains of the aquatic fern Salvinia natans (L.) All. have been found in several early medieval sites in Gdańsk, N. Poland. This record indicates a population expansion
of this species around 7th–8th century A.D., similar to the recently observed rapid spread and high population dynamics of
S. natans in northern Poland, which recent studies have attributed to climate warming. Our results suggest that in the Vistula deltaic
area the S. natans expansion in the Early Middle Ages (7th–8th century A.D.) was similarly stimulated by climate warming, while its subsequent
decline was mainly due to climate cooling, especially during the Little Ice Age. Warmer winters and springs and a longer growing
season seem to be the most important factors forcing the expansion of S. natans in medieval times. According to our data, the co-occurrence of S. natans with other aquatic plant species was similar in both the medieval and present-day vegetation. Also, the high density of S. natans in the medieval population caused impoverishment of the local ecosystems in a way that has been observed in recent water
bodies affected by invasive pleustophytes (free-floating plants). 相似文献
83.
84.
This paper presents a method, which has been recently developed in the Department of Agrometeorology of the Poznań Agricultural University, for estimating heat balance components based on standard meteorological data, plant development stage, and land-use conditions. Estimates of latent heat flux components made it possible to obtain values of areal evapotranspiration and surface runoff. The method was applied in four catchment areas in Central Poland under present climatic conditions as well as under new, expected climatic conditions caused by an increase of ‘greenhouse gases’ in the atmosphere. Some changes in land use were also considered. The results show significant changes in the water balance when comparing present and future conditions of precipitation and evapotranspiration. 相似文献
85.
Measurement results of PM10 (particulate matter with diameters below 10 μm) concentrations performed at four stations in central Poland (2007–2010) were analyzed in terms of levels and distributions of concentrations, the number of exceedances of the limit values and the causes of these exceedances. PM10 levels were similar at suburban and rural stations, except of one station located in the vicinity of a busy street. The median of PM10 concentration ranged from 26 μg/m3 at suburban station to 44 μg/m3 at Warsaw Kerb station. Seasonal variability analysis of PM10 concentration revealed an additional maximum beyond the usual autumn-winter one. This maximum occurred in April at all stations, and corresponded to seasonal wildfires activity and dust activation in Eastern Europe. Cluster analysis of back-trajectories revealed that PM10 concentrations depend on the direction of advection of the incoming air; the highest values are registered for air of regional and southern origins, while the lowest are for the airmasses coming from the north and northwest direction. 相似文献
86.
Janusz Eluszkiewicz 《Icarus》2004,170(1):234-236
The thickness of a porous regolith on Europa is estimated to be ∼1 km. Provided that this regolith contains as little as 1% by volume of cavities with sizes comparable to the radar wavelength, its presence poses an insurmountable obstacle in the search for Europa's ocean by means of a sounding radar. 相似文献
87.
AbstractThe solar backscattered ultraviolet (SBUV/SBUV-2) merged ozone datasets, version 8.6, including column ozone and ozone profiles for the 1979–2012 period are examined for the 35°N–60°N zonal belt in the northern hemisphere mid-latitudes and four sub-regions: central Europe, continental Europe, North America, and East Asia. The residual long-term patterns for total ozone and ozone profiles are extracted by smoothing the time series of differences between the original and the modelled ozone time series. Modelled ozone is obtained using the standard trend model accounting for ozone variability due to changes in stratospheric halogens and various dynamical factors commonly used in previous ozone trend analyses. Since about 2005 spring and summer total ozone in the troposphere and lower stratosphere has decreased in some regions (central and continental Europe, North America, and the 35°N–60°N zonal belt) compared with modelled ozone. The negative departure from modelled ozone in 2010 is approximately 2–3% of the overall 1979–2012 monthly mean level. It seems that this decrease is a result of yet unknown dynamical processes rather than to chemical destruction because the differences have a longitudinal structure, and total ozone in the upper stratosphere still follows changes in stratospheric halogen loading. 相似文献
88.
Karol Kuliński Joanna Święta-Musznicka Andrzej Staniszewski Janusz Pempkowiak Małgorzata Latałowa 《Journal of Paleolimnology》2007,38(4):555-567
The quantity and quality of lignin phenols (Σ8, Λ, S/V, C/V and (Ad/Al)v) in the sediments of three small Lobelia lakes with neither inlets nor outlets were investigated and compared with palynological data and lithology of the profiles.
The method of alkaline CuO oxidation was used. Substantial differences with respect to sedimentary lignin concentration and
provenance recorded along the profiles and among the sites are in good agreement with pollen data describing the dominant
type of vegetation and with indices of soil erosion in the lakes’ catchments. This relation shows that the compositions of
lignin degradation products in these lakes are closely related to the local environmental conditions. In all the lakes gymnosperm
wood is the main source of lignin products; however, each lake is characterized by different S/V index values. Especially
good correlations were obtained between pine pollen proportions in sediments and the S/V index. The correlation between the
C/V and (Ad/Al)v indices indicates a higher degradation of organic matter when non-woody tissue is more abundant. This pilot study illustrates
the usefulness and potential for a wider application of lignin oxidation products in palaeoecological reconstructions. This
kind of data would be of special importance when investigating local presence/absence of woody plants and the role of angiosperms/gymnosperms
in local vegetation. Estimates of lignin biodegradation levels, as well as the data on diagenetic processes, may afford supplementary
information on possible disturbances in sedimentation. 相似文献
89.
Janusz A. Gil David G. Khechinashvili & George I. Melikidze 《Monthly notices of the Royal Astronomical Society》1998,298(4):1207-1211
The famous neutron star Geminga was until quite lately the only pulsar undetected in the radio regime, though observed as a strong pulsating γ- and X-ray source. Three independent groups from the Pushchino Radio Astronomy Observatory (Russia) reported recently the detection of pulsed radio emission from Geminga at 102.5 MHz, i.e., the first detection of the radio pulsar PSR J0633 + 1746 by Kuz'min &38; Losovskii, Malofeev &38; Malov and Shitov &38; Pugachev. This pulsar exhibits the weakest radio luminosity known. Its average pulse profile appears to be very wide, filling an entire 360° pulse window according to Kuz'min &38; Losovskii. We present a model explaining the peculiarities of the Geminga radio pulsar, based on the assumption that it is an almost aligned rotator. The electromagnetic waves generated in the inner magnetosphere reach the region within the light cylinder with a weak magnetic field (at distances of a few light cylinder radii), where they are strongly damped due to the cyclotron resonance with particles of magnetospheric electron–positron plasma. The lowest frequencies that can escape are determined by the value of the magnetic field in the region where the line of sight passes through the light cylinder. The specific viewing geometry of an almost aligned rotator implies that the observer's line of sight probes the emission region near the bundle of the last open field lines. This explains the unusually weak emission from Geminga's low-frequency radio pulsar. 相似文献
90.
Sergio Castro Jorge Goldfarb Janusz Laskowski 《International Journal of Mineral Processing》1974,1(2):141-149
The rate and extent of the heterogeneous reaction that takes place between dissolved sodium sulphide and synthetic tenorite is studied for a wide range of sodium sulphide to copper oxide ratios. Besides the sulphidization with the formation of a copper-sulphide layer, a substantial oxidation of sulphide ions takes place at the surface of the solid. The extent of both types of reactions is quantitized by combining specific analytical methods.The results are discussed in terms of possible mechanisms and of their implications in the sulphidization process applied in the flotation of oxidized copper ores. 相似文献