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21.
Eugen Vujić Giuliana Verbanac Stanislav Francisković-Bilinski Vladis Vujnović Antun Marki 《Studia Geophysica et Geodaetica》2011,55(1):175-190
Based on the ground survey of total-field magnetic data at 53 sites, which recorded a time-series over the interval 2003–2005,
the core field + long wavelength lithospheric field over the middle-northern Croatia region was calculated. The area of the
survey was 18900 km2, an average distance between the neighbouring sites being 12 km. The results were reduced to 2004.5 epoch. This “normal”
total-field was estimated using the firstorder Taylor polynomial as a function of geographic coordinates, and the polynomial
coefficients were calculated with three methods of adjustment: simple and weighted least squares fits and adjustment according
to the most frequent value. The stability of the normal field was tested using the Monte Carlo-type test, by decreasing the
input data set in each adjustment (up to 90%). All obtained field residuals (measured-“normal”) were mutually compared, as
well as fit coefficients of the Taylor polynomials. The residual values indicate the presence of shorter-wavelength anomalies,
specifically three major residual anomalies were found (−106 nT, 74 nT and 57 nT). The geostatistical analysis of the ground
survey data and the normal field residuals (respectively), using the median absolute deviation method, was further conducted
in order to evaluate the calculated anomalies. The geological situation around the anomalies derived by the median absolute
deviation method, and around the normal field residual anomalies, is given. The correlation was found between higher value
anomalies of the normal field residuals, and shallow volcanic rocks and oil field, respectively. 相似文献
22.
In this paper the spatial and temporal responses of the Some?u Mic River (Romania) to natural and anthropogenic controls over the past 150 years are analysed, based on a series of morphometric parameters extracted from five successive sets of topographic maps and one set of orthophotos. Prior to the intensive hydrotechnical interventions of the last four decades, the river was characterized by a complex alternation of different channel types, resulting in a mixture of alluvial and mixed sinuous – meandering – sinuous anabranched – meandering anabranched reaches, each a few hundred metres to a few kilometres long. The main cause for this spatial behaviour was the local geology. Its effects were intensified by a larger scale slope, slightly higher than along a longitudinal profile with normal concavity, as a consequence of the presence of a 400 m elevation knick‐point located in the catchment area. A generalized maintenance of river in the floodplain perimeter during the entire interval of study (centennial scale), with local planform adjustments and lack of median scale avulsion in lateral tilting areas and along the anabranched reaches, channel lengthening and meander development during hydrological stable periods and channel shortening and increasing of natural cutoffs during periods with higher incidence of floods (decadal scale), and the incapacity of local morphologic changes resulted from human interventions to completely counterbalance general trends (decadal scale), supports the idea of decreasing the amplitude and frequency of important floods, after the end of the Little Ice Age. Channel metamorphosis by canalization, diminishing/elimination of overflows and medium‐scale avulsions by changes in flow regimes (dams) and the presence of dykes in the floodplain perimeter, channel narrowing (43%) and incision (at least after 1945) downstream from dams, and probably because of in‐channel gravel mining are the main anthropically induced changes along the Some?u Mic River. Even if human impact is important, both at the drainage basin scale and along the Some?u Mic River, it has only local impacts, subordinated to climate. The low level of human impact on this river could be the consequence of the higher general slope downstream from 400 m elevation knick‐point, which probably forces the positioning of its effects under an important internal threshold of the fluvial system. This boundary condition defines Some?u Mic River as an atypical river. This study supports the idea that climate has a more important role in the post‐Little Ice Age (LIA) rivers' behaviour than currently accepted. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
23.
Tamás Váczi Lutz Nasdala Richard Wirth Mathias Mehofer Eugen Libowitzky Tobias Häger 《Mineralogy and Petrology》2009,97(1-2):129-138
Zircon samples without and with secondary chemical alteration from diverse sources were subjected to heat treatment at 1400 °C for 96 h. Resulting new phases and textures suggest that decomposition of zircon into component oxides occurred in all experiments to various degrees. The crucible material was found to have a strong influence on the extent of breakdown, especially in the case of altered starting materials. In this study the progressive stages of the breakdown of zircon grains are described. The factors that may govern the decomposition are discussed, including radiation damage, secondary alteration and external reaction conditions (sample container, atmosphere). Alumina crucibles should generally be avoided in dry annealing of zircon, to minimise uncontrolled breakdown into oxides. 相似文献
24.
Adina-Laura Lazăr Călin Baciu Carmen Roba Tiberius Dicu Cristian Pop Călin Rogozan Cristina Dobrotă 《Environmental Earth Sciences》2014,72(11):4653-4666
The paper presents the results of a combined soil and vegetation survey in Ro?ia Montan? mining area (western Romania), famous for its gold and silver deposits, extensively exploited over the last 2,000 years. As the ore extraction has ceased in 2006 and new operations could be initiated in the future, the study contributes to the definition of the environmental baseline. Samples of topsoil and leaves of the tree species Betula pendula and Carpinus betulus have been collected from the inside and outside of the mining area, on a total surface of more than 60 km2. The pH and heavy metal concentrations (Cd, Cr, Cu, Ni, Pb, and Zn) have been measured on 262 soils/sediments samples, revealing the predominantly acidic character of soils and the generally low contents of heavy metals. Stronger acidity and higher contents of heavy metals have been noticed in the proximity of the mining site, on the tailings and waste rock dumps, and along the streams with acid water. More than 100 leaf samples have been analysed for the same heavy metals as soils and also for chlorophyll fluorescence and pigment concentrations. B. pendula has shown a particular ability to concentrate Zn in leaves, at levels that may greatly exceed the Zn content in the corresponding soil samples. The correlation between the heavy metal contents in leaves and in soils, in most of the cases, is not very strong, presumably in relation to the low concentrations in soils. The chlorophyll concentration in leaves of B. pendula slightly diminishes on soils with low pH. 相似文献
25.
26.
Vasile Muntean Radu Crisan Daniela Paşca Stefan Kiss Mihail Drăgan-Bularda 《International Journal of Salt Lake Research》1996,5(1):35-44
Sediments of 56 salt lakes from Romania were studied enzymologically. The following 7 enzymatic and nonenzymatic catalytic activities have been measured: phosphatase, H2O2-splitting in nonautoclaved (catalase) and autoclaved samples, TTC reduction in nonautoclaved (dehydrogenase) and autoclaved samples, without or with glucose addition. A formula is proposed for the evaluation of the enzymatic potential of salt lake sediments or other habitats. A hierarchy of the studied lakes has been established on the basis of the enzymatic potential of their sediments expressed as enzymatic indicator. 相似文献
27.
Spectroscopic and bond-topological investigation of interstitial volatiles in beryl from Slovakia 总被引:1,自引:0,他引:1
Jana Fridrichová Peter Bačík Valéria Bizovská Eugen Libowitzky Radek Škoda Pavel Uher Daniel Ozdín Martin Števko 《Physics and Chemistry of Minerals》2016,43(6):419-437
Nine beryl samples from Western Carpathians, Slovakia, were investigated by infrared and Raman spectroscopy and differential thermal analysis. Two types of water H2O I and H2O II were detected. Infrared spectroscopy proved the presence of water type I and II in the presence of alkali cations with several bands: (1) symmetric stretching vibration—ν1; (2) antisymmetric stretching mode—ν3; (3) bending vibration—ν2. The presence of singly and doubly coordinated type II water (IIs and IId) was confirmed by single-crystal IR spectroscopy. From Raman spectra a band at 3606 cm?1 was assigned to ν1 of water type I and the range of 3597–3600 cm?1 to water type II. The presence of doubly coordinating water indicates a relatively highly hydrated environment with the presence of alkali ions including Na as the dominant cation coordinated by H2O II. CO2 bands were detected only by single-crystal IR spectroscopy. Thermal analysis proved total water loss in the range of 1.4–2.0 wt% and three main dehydration events. Based on the study of bond-topological arrangements two molecules of H2O IId are each bound with two H···O1 bonds and one Na–OW bond with an angular distortion, and by releasing one H2O molecule more stable H2O IIs is produced. The H2O I molecule is bound only by two equivalent hydrogen bonds. The H2O IIs molecule with a Na–OW bond strength of 0.28 vu and two H···O1 bonds of 0.14 vu without any forced angular distortion is the most stable of all. 相似文献
28.
Anke Watenphul Eugen Libowitzky Bernd Wunder Matthias Gottschalk 《Physics and Chemistry of Minerals》2010,37(9):653-664
The OH site in topaz is investigated by IR spectroscopy depending on the OH concentration and temperature. The two OH bands
that can be distinguished are due to the local ordering of F and OH in opposite sites of the crystal structure. The first
typical sharp band stems from OH groups with fluorine in the opposite (=acceptor) site. The second band occurs as a shoulder
on the low-energy wing and is related to two opposite OH groups. The degree of local OH–OH ordering depends on the OH concentration
and, due to statistical F/OH distribution, can be predicted by probability calculations. The substitution of OH for F has
a non-linear effect on the increase of the lattice parameters. An autocorrelation analysis of the IR spectra revealed two
temperature-induced phase transitions. At −135°C, the local symmetry changes from P1 to Pbn21, although this change involves only the H atoms. The transition from Pbn21 to Pbnm at 160°C is caused by changes of the local F/OH ordering in the crystal structure. 相似文献
29.
Sans résumé 相似文献
30.
Polarized FTIR spectra of near endmember forsterite single crystals from Pamir, Tadzikistan show the existence of sharp strongly pleochroic absorption bands in the region of the OH stretching fundamental. Bands centered at 3674/3624, 3647/3598 and 3640/ 3592 cm-1 are attributed to OH dipoles oriented parallel to [100]. An OH band doublet at 3570/3535 cm-1 shows both, a strong absorption parallel to [100] and a strong component parallel to [001]. On the basis of the pleochroic scheme and under the assumption of vacancies on Si- and M-sites it is proposed that O1 is partially replaced by OH defects pointing to the vacant Si-site. O3 is donator oxygen of OH dipoles lying near the O3-O1 tetrahedral edge or roughly pointing to a vacant M2-site. Also O2 can act as donator oxygen of an OH group oriented along the O2-O3 edge of a vacant M1 octahedron. The splitting of the bands is explained by the presence of Fe2+ in cation sites surrounding the OH defects. 相似文献