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1.
Baidyanath Chattopadhya 《Pure and Applied Geophysics》1972,98(1):65-71
Summary Rotatory vibrations of a thick spherical shell of isotropic non-homogeneous material with rigidity and density given by (i) =
0
r
-2 withQ =Q
0
r
-2
e
2mr
and (ii) =
0
r
m with =Q
0
r
n have been discussed and the frequency equation is derived with numerical enumeration of frequency in each case. 相似文献
2.
The role of phosphorus in phytoplankton growth was studied in Lake Vesijärvi, a large previously eutrophic body of water with a history of flourishing fishery. The study combined different approaches: long-term algal enrichment experiments with natural phytoplankton assemblages were carried out together with observations on nutrient and chlorophyll a concentrations, elemental ratios (N:P, C:P, C:N) of particulate matter, and analysis of P uptake using [33P]. None of the approaches revealed periods of P limitation, but some growth experiments as well as elemental ratios indicated slight deficiency in early summer. Concentrations of total dissolved phosphorus (TDP), which were usually 20–30 g l–1, also indicated luxurious P resources. Thermal stratification was weak and the lake mixed twice during the study period; this was reflected in the phytoplankton biomass that increased up to 4-fold. Results of elemental ratios usually suggested the occurrence of nitrogen limitation, and in general these ratios were low for a lake. All size fractions >0.22 m in the experiments with [33P] showed P uptake. In August most of the P was taken up by picoplankton, but when the lake turned over in September, the uptake of P by this fraction was absent. Thus, there was always a plentiful supply of P for phytoplankton, but the shortage of inorganic N may have affected those algae not capable of fixing N2. These conditions should have favoured the growth of heterocystous cyanobacteria, but these prokaryotes never attained high abundances. This may have been due to the weak stability of the water column, or the growth of cyanobacteria may have been limited by trace elements such as molybdenum or iron. 相似文献
3.
Roland Psenner 《Aquatic Sciences - Research Across Boundaries》1989,51(2):108-128
Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 eq 1–1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization. 相似文献
4.
5.
The amplitude response of a LCR gravimeter with the SRW-E feedback was determined on a vertical vibrating platform. The ink-pen recorder was connected parallel with the digital voltmeter input to obtain an analog response of the gravimeter to the harmonic motion of the base with a peak-to-peak amplitude of 10 m and periods excited in an interval of 4 - 10 s as by the ground motion of meteorological microseisms, and in the interval 10 -100 s as by surface waves of distant strong earthquakes.
In the first interval, an unexpected maximum of the amplitude response was observed with the double amplitude of apparent 6,5 Gal (6.5 × 10
–8
m/s
2
) at a period of 4.8 s, and a baseline shift with the amplitude of–64Gal was observed at the same period. The value of this direct component cannot be separated from the effect of the Earth's gravity field. In the second interval, the amplitude response of the gravimeter displayed one expected maximum at a period of 40 s with the double amplitude of 8.1Gal. At the usual level of microseisms with a peak-to-peak amplitude of up to 2 m the fluctuation of the gravimeter on the direct baseline shifted by –4.9 Gal was estimated at 1 Gal. With typical Rayleigh surface waves with periods of 20 s and double amplitudes of up to 100 m, the fluctuation reached 67 Gal. 相似文献
6.
R. A. Müller M. N. Futter S. Sobek J. Nisell K. Bishop G. A. Weyhenmeyer 《Aquatic Sciences - Research Across Boundaries》2013,75(4):535-545
The character of organic carbon (OC) in lake waters is strongly dependent on the time water has spent in the landscape as well as in the lake itself due to continuous biogeochemical OC transformation processes. A common view is that upstream lakes might prolong the water retention in the landscape, resulting in an altered OC character downstream. We calculated the number of lakes upstream for 24,742 Swedish lakes in seven river basins spanning from 56º to 68º N. For each of these lakes, we used a lake volume to discharge comparison on a landscape scale to account for upstream water retention by lakes (Tn tot). We found a surprisingly weak relationship between the number of lakes upstream and Tn tot. Accordingly, we found that the coloured fraction of organic carbon was not related to lake landscape position but significantly related to Tn tot when we analysed lake water chemical data from 1,559 lakes in the studied river basins. Thus, we conclude that water renewal along the aquatic continuum by lateral water inputs offsets cumulative retention by lakes. Based on our findings, we suggest integrating Tn tot in studies that address lake landscape position in the boreal zone to better understand variations in the character of organic carbon across lake districts. 相似文献
7.
Summary This paper studies the propagation of Surface Waves on a spherically aeolotropic shell surrounded by vacuum. The elastic constantsc
ij and density of the material of the shell are assumed to be of the form
ij
r
l and
o
r
m respectively, where
ij
o are constants andl, m are any integers. 相似文献
8.
Summary Based on the qualitative microspectrophotometric analysis of 287 atmospheric dust samples taken within the surface boundary layer over south central New Mexico, U.S.A. from May 1966 through October 1967, a representative infrared absorption spectrum from 4000 to 250 cm–1 (2.5 to 40 m) is presented. The strongest absorption band is centered at 1027 cm–1 (9,7 m), within the 1250 to 770 cm–1 (8 to 13 m) atmospheric window, and is silicate induced. Two other strong broad absorption bands are the carbonate band at 1425 cm–1 (7.0 m) and the silicate band at 468 cm–1 (21.4 m). Temporal variations in the absorption spectra of the dust are observed primarily in the varying relative intensities of the 1027 and 1425 cm–1 (9.7 and 7.0 m) absorption bands and in the occasional enhancement of the 1027 cm–1 (9.7 m) band caused by sulfates in the dust. This study indicates that there is a close similarity between the absorption spectra of the atmospheric dust and the spectra of the small particle fraction of area soils, and between the representative dust spectrum and a spectrum of a synthetic mixture (by weight) of 80% silicates, 16% carbonates, and 4% nitrates. 相似文献
9.
Monthly collections of phytoplankton were supported by physical–chemical data and measures of chlorophyll a concentrations in the search for particular environmental factors that could explain the constant presence of desmids in a Mexican tropical lake, a characteristic not common among the phytoplanktic communities of Mexican lakes. Samplings were taken from the water column in the deepest part of the lake (40 m) and intensified in the metalimnetic zone, whose establishment was monitored by observations of temperature and oxygen profiles. The general behavior of Lake Zirahuén was typical of warm monomictic tropical lakes at high elevation: a short mixing phase during the hemispheric winter. The depth of ZMIX and Zeu revealed a well-illuminated epilimnion, suggesting that phytoplankton communities are not likely to be light-limited. The oligotrophic nature of the lake is indicated by discrete concentrations of inorganic nutrients, PTOT in the interval of 0.01–0.03 mg l−1 and chlorophyll a between 0.23 and 3.98 μg l−1. These characteristics together with a low concentration of calcium, define a lacustrine environment different from other Mexican lakes, and one that could be suitable for desmids communities. 相似文献
10.
Summary A comparison has been made between the Townsend primary ionization coefficient, , for dry air and for air with humidities typical of those in the atmosphere. is defined as the number of new electrons produced by an electron per centimeter of drift in a field. A range of field/pressure ratios,E/p
0, of 40 to 100 V (cm torr)–1 was employed. The variation of with humidity is very small.Over the range ofE/p
0 from 50 to 100 V (cm torr)–1, the secondary ionization coefficient, , of a water surface has been found from sparking potential data to be typically 2×10–4. represents the fraction of primary ionizing collisions that ultimately result in the production of additional electrons at the surface. 相似文献
11.
Věra Vaňková Vladislav Babuška Reviewer J. Fiala 《Studia Geophysica et Geodaetica》1972,16(4):383-392
Summary The coefficient of the gamma-ray absorption
Cs
137
investigated in eclogites of the Bohemian Massif varies with fresh samples from0.2477 cm
–1
to 0.2804 cm
–1
. Symplectite is the main factor decreasing the value of down to0.242 cm
–1
. On the contrary, the coefficient increases with the increasing content of clinopyroxene and especially of garnet. The linear dependence of the coefficient on the density may be expressed by the equation =0.0682+0.028. 相似文献
12.
This study investigated two mining lakes located in the north of Lower Austria. These lakes arose 45 years ago when open cast lignite mining ceased. The lakes are separated by a 7-m wide dam. Due to the oxidation of pyrite, both lakes have been acidified and exhibit iron, sulphate, and heavy metal concentrations several orders of magnitude higher than in circumneutral lakes. The water column of both lakes is divided into two layers by a pronounced chemocline. The smaller mining lake (AML), with pH close to of 2.6, is the most acidic lake in Austria, whereas flooding with stream water and by drainage from the surrounding fields neutralized the adjacent larger pit lake. The goal of our study was to investigate the effect of flooding on its physical, chemical and biological properties, in comparison to the pristine AML. Even relative to other extremely acidic lakes, the flora and fauna in the AML was reduced and composed of only two flagellate, one ciliate, and one rotifer species. The simplified pelagic food web in the mixolimnion consisted of heterotrophic bacteria, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp., and the rotifer Cephalodella sp. The latter two are as yet undescribed new species. The heliozoan Actinophrys sp. that may act as top predator occurred only in low abundance. The euglenid Lepocinclis buetschlii formed a stable deep chlorophyll maximum (DCM) at 7 m depth. Highest cell numbers of L. buetschlii in the DCM exceeded 108 L?1. The neutralized mining lake harboured higher plankton diversity similar to that of natural circumneutral lakes. A peak of at least 16 different phytoplankton taxa was observed during summer. The zooplankton consisted of several copepod species, daphnids and other cladocerans, and at least six different rotifer species. Several fish species occurred in the neutralized lake. Although the effect of non-permanent flooding was largely sustainable, interannual fluctuations of the pH affected the plankton community and reduced its species diversity. 相似文献
13.
Layers of artificial granite gouge have been deformed on saw-cut granite surfaces inclined 30° to the sample axes. Samples were deformed at a constant confining pressure of 250 MPa and temperatures of 22 to 845°C. The velocity dependence of the steady-state coefficient of friction (ss) was determined by comparing sliding strengths at different sliding rates. The results of these measurements are consistent with those reported bySolberg andByerlee (1984) at room temperature andStesky (1975) between 300 and 400°C. Stesky found that the slip-rate dependence of (ss) increased above 400°C. In the present study, however, the velocity dependence of (ss) was nearly independent of temperature. 相似文献
14.
Tibor Boldizsár 《Pure and Applied Geophysics》1967,67(1):128-132
Summary Latest measurements of terrestrial heat flow in the Hungarian and Russian parts of the Carpathian basin confirm previously measured high flow values between 2.0–3.3 cal/cm2 sec. Recent measurement in the Permian anticline structure of the Mecseck. Mts. in Hungary gave 2.4 cal/cm2sec, whereas in the Russian part of the basin, near to the Hungarian border 2.6 cal/cm2 sec was measured in Miocene sediments. For more than 100000 km2 surface of the Carpathian basin covered by Hungary and parts of Slovakia and Russian the high heat flow is an established fact. 相似文献
15.
Protozoan communities developed in laboratory microecosystems were used to evaluate the toxic effects of lead ion. The lead was added as lead acetate in different concentrations (50 g · l–1, 20 g · l–1, 10 g · l–1 and 1 g · l–1). The protozoans were taxonomically identified and classified into functional groups according to their common nutritional type. The population dynamics of protozoa has been studied. In the control the most frequent groups were bacterivore-detritivores and photosynthetics (more than 75% of abundance). Noticeable lead effects were observed after 24 hours of exposure to metal in all fractions. In general, the lead caused reductions in the number taxa, in total protozoan abundance and in protozoan biomass. The diversity values decreased in more than two nep respect to control in the different fractions. At the end of assay, the protozoan communities structure was simplified in the fractions with lead and some species of little flagellates were dominant. The information provided by this microecosystems of protozoan community was more complex than the one provided by single-species bioassays. Community protozoan bioassays may give more information about the toxic effects to compare with actual ecosystems. 相似文献
16.
Perturbations of the lake water balance, inputs of heavy metals to lakes, and intensifying fertilization of lakes through
input and accumulation of phosphorus—these three classes of phenomena are among the more important background processes in
lake restoration. Lake restoration consists of a series of measures animed at producing a homeostatic response of a lake system
to external perturbations. The success of its implementation is affected by the morphometric and edaphic parameters of different
types of lakes. The relationship between the volume (V) and mean-depth
of fresh-water lakes indicates a trend of
. Glacial lakes occuring on or near crystalline shields have relatively shallow depths, whereas volcanic lakes, rift valley
and deep valley lakes have relatively greater depths for the same volume. For saline lakes (21 lakes, V>1 km3) that undergo cycles of expansion and shrinkage, the V to
relationship is closer to power 1. Water residence times (τ) of small and big fresh-water lakes show a trend of τ approximately
linear in
or τ∝V0.3. Volcanic lakes and Maare have longer residence times in comparison to other lakes of similar volumes. For the major inorganic
chemical species and heavy metals, the regulatory upper-limit concentrations in drinking water in the USA and EEC are from
several times to more than 100 times higher than their concentrations in a global mean river water. Only three elements (Fe,
P, and Al) occur in river water at concentrations approaching such upper-limit recommendations. Rates of accumulation of phosphorus
in lake water and sediments, computed as the difference between input and ouflow removal rates for 23 fresh-water lakes, are
generally lower for lakes of longer water residence time. The rate of accumulation is a measure of homeostatic response of
the lake system to input load: it is equivalent to the rate of all the removal processes needed to maintain phosphorus concentration
in lake water at a steady state. 相似文献
17.
The effects of sliding velocity on the frictional and physical properties of heated fault gouge 总被引：2，自引：0，他引：2
The frictional properties of a crushed granite gouge and of gouges rich in montmorillonite, illite, and serpentine minerals have been investigated at temperatures as high as 600°C, confining pressures as high as 2.5 kbar, a pore pressure of 30 bar, and sliding velocities of 4.8 and 4.8×10–2 m/sec. The gouges showed nearly identical strength behaviors at the two sliding velocities; all four gouges, however, showed a greater tendency to stick-slip movement and somewhat higher stress drops in the experiments at 4.8×10–2 m/sec. Varying the sliding velocity also had an effect on the mineral assemblages and deformation textures developed in the heated gouges. The principal mineralogical difference was that at 400°C and 1 kbar confining pressure a serpentine breakdown reaction occurred in the experiments at 4.8×10–2 m/sec but not in those at 4.8 m/sec. The textures developed in the gouge layers were in part functions of the gouge type and the temperature, but changes in the sliding velocity affected, among other features, the degree of mineral deformation and the orientation of some fractures. 相似文献
18.
M. Meybeck P. Blanc A. E. Moulherac C. Corvi 《Aquatic Sciences - Research Across Boundaries》1991,53(4):273-289
Regular surveys of bottom water chemistry (SiO2, O2, Fe, Mn) have been carried from 1978 to 1986 in the deepest 30 m of Lake Léman (max. depth 309 m) including interface waters sampled with a Jenkins Mortimer corer. When compared to normal chemical gradients near bottom, i.e. O2 decrease and SiO2 increase, three types of anomalies (lens, interface, and behaviour) have been observed on O2 and SiO2, the most sensitive chemical species. These anomalies were found throughout the year, in several stations of the deepest part of the lake and even along the slope of the lake basin. Major anomalies (O2 + 3 to 10 mg ·l–1; SiO2 -1 to 2 mg·l–1) were generally found at the sediment water interface and may extend 10–20 m above the sediment and last 10 weeks. Others marked lens anomalies could be observed for 3 to 4 months. Several mechanisms are probably responsible for this injection of surface waters along the lake slope (accumulation of turbid water on lake banks after severe windstorms; river density currents due to temperature and/or turbidity difference with lake waters). These water-inputs do not represent important volumes ( 1% total lake volume) but, when occuring at the interface, they ensure a sufficient oxygen level to prevent diffusion of phosphate and ammonia from pore waters when winter lake overturns do not reach bottom layers (from 1972 to 1980). Complete overturns, as observed in 1980/81, are connected with major interface anomalies (bottom O2 moves up from 2 to 10 mg·l–1) occuring before surface mixing reaches the deepest layers. 相似文献
19.
Summary This paper discusses the disturbance produced in an infinite layer of non-homogeneous elastic material characterised by =0 n and =0n(n>0) where and are the density and shear modulus respectively of the material, due to periodic torsional force applied on the wall of a cylindrical hole in the layer. The variation of the displacement component with the radius vector is shown graphically and compared with the corresponding homogeneous case. 相似文献
20.
Nanina Blank Alan G. Hudson Pascal Vonlanthen Ole Seehausen Chad R. Hammerschmidt David B. Senn 《Aquatic Sciences - Research Across Boundaries》2013,75(2):261-273
Central European lake whitefish (Coregonus spp.) colonized Swiss lakes following the last glacial retreat and have undergone rapid speciation and adaptive radiation. Up to six species have been shown to coexist in some lakes, and individual species occupy specific ecological niches and have distinct feeding and reproductive ecologies. We studied methylmercury (MeHg) accumulation in sympatric whitefish species from seven Swiss lakes to determine if ecological divergence has led to different rates of MeHg bioaccumulation. In four of seven lakes, sympatric species had distinctly different MeHg levels, which varied by up to a factor of two between species. Generally, species with greater MeHg levels were smaller in body size and planktivorous, and species with lower MeHg were larger and benthivorous. While modest disparities in trophic position between species might be expected a priori to explain the divergence in MeHg, δ15N of bulk tissue did not correlate with fish MeHg in five of seven lakes. Results of a nested ANCOVA analysis across all lakes indicated that only two factors (species, lake) explained substantial portions of the variance, with species accounting for more variance (52 %) than inter-lake differences (32 %). We suggest that differences in MeHg accumulation were likely caused by diverging metabolic traits between species, such as differences in energy partitioning between anabolism and catabolism, potentially interacting with species-specific prey resource utilization. These results indicate substantial variability in MeHg accumulation between closely related fish species, illustrating that ecological speciation in fish can lead to divergent MeHg accumulation patterns. 相似文献