Petrological, geochemical and isotopic characteristics of the lithospheric mantle beneath Sardinia (Italy) as indicated by ultramafic xenoliths enclosed in alkaline lavas     

Ivana Rocco  Michele Lustrino  Vincenzo Morra  Leone Melluso 《International Journal of Earth Sciences》2012,101(5):1111-1125

Mantle xenoliths hosted in Miocene-Quaternary mafic alkaline volcanic rocks from Sardinia have been investigated with electron microprobe, laser ablation microprobe-inductively coupled plasma-mass spectrometry and thermal ionization mass spectrometry techniques. The xenoliths are anhydrous clinopyroxene-poor lherzolites and harzburgites, plus very rare websterites and olivine-websterites. Glassy pods having thin subhedral to euhedral microlites of olivine, clinopyroxene and spinel have been found in harzburgites and websterites. Clinopyroxene shows trace element variability, with values of (La/Yb)_N ranging from sub-chondritic (0.01) to supra-chondritic (8.6). The Sr–Nd isotopic ratios of the clinopyroxenes fall mostly in the field of the European lithospheric mantle xenoliths (⁸⁷Sr/⁸⁶Sr from 0.70385 to 0.70568 and ¹⁴³Nd/¹⁴⁴Nd ranging from 0.512557 to 0.512953). The geochemical characteristics of the Sardinian xenoliths testify to the variable degrees of earlier partial melt extraction, followed by metasomatic modification by alkaline melts or fluids. Websterites are considered to represent small lenses or veins of cumulitic (i.e. magmatic) origin within the mantle peridotite.  相似文献   

Crystal structure of meteoritic schreibersites: determination of absolute structure     

Roman Skála  Ivana Císařová 《Physics and Chemistry of Minerals》2005,31(10):721-732

Minerals of the schreibersite–nickelphosphide series (Fe,Ni)₃P crystallize in the non-centrosymmetric space group . As a consequence, they can possess two different spatial arrangements of the constituting atoms within the unit cell, related by the inversion symmetry operation. Here, we present the crystal structure refinements from single crystal X-ray diffraction data for schreibersite grains from iron meteorites Acuña, Carlton, Hex River Mts. (three different crystals), Odessa (two different crystals), Sikhote Alin, and Toluca aiming for the determination of the absolute structure of the examined crystals. The crystals studied cover the composition range from ~58 mol% to ~80 mol% Fe₃P end-member. Unit-cell parameter a and volume of the unit cell V, as well as certain topological structural parameters tightly correlate with Fe₃P content. Unit-cell parameter c, on the other hand, does not show such strong correlation. Eight of the nine crystal structure refinements allowed unambiguous absolute structure assignment. The single crystal extracted from Toluca is, however, of poor quality and consequently the structure refinement did not provide as good results as the rest of the materials. Also, this crystal has only weak inversion distinguishing power to provide unequivocal absolute structure determination. Six of the eight unambiguous absolute structure determinations indicated inverted atomic arrangement compared to that reported in earlier structure refinements (here called standard). Only two grains, one taken from Odessa iron and the other from the Hex River Mts. meteorite, reveal the dominance of standard crystal structure setting.  相似文献   

Extreme daily precipitation: the case of Serbia in 2014     

Tošić  Ivana  Unkašević  Miroslava  Putniković  Suzana 《Theoretical and Applied Climatology》2017,128(3-4):785-794

The extreme daily precipitation in Serbia was examined at 16 stations during the period 1961–2014. Two synoptic situations in May and September of 2014 were analysed, when extreme precipitation was recorded in western and eastern Serbia, respectively. The synoptic situation from 14 to 16 May 2014 remained nearly stationary over the western and central Serbia for the entire period. On 15 May 2014, the daily rainfall broke previous historical records in Belgrade (109.8 mm), Valjevo (108.2 mm) and Loznica (110 mm). Precipitation exceeded 200 mm in 72 h, producing the most catastrophic floods in the recent history of Serbia. In Negotin (eastern Serbia), daily precipitation of 161.3 mm was registered on 16 September 2014, which was the maximum value recorded during the period 1961–2014. The daily maximum in 2014 was registered at 6 out of 16 stations. The total annual precipitation for 2014 was the highest for the period 1961–2014 at almost all stations in Serbia. A non-significant positive trend was found for all precipitation indices: annual daily maximum precipitation, the total precipitation in consecutive 3 and 5 days, the total annual precipitation, and number of days with at least 10 and 20 mm of precipitation. The generalised extreme value distribution was fitted to the annual daily maximum precipitation. The estimated 100-year return levels were 123.4 and 147.4 mm for the annual daily maximum precipitation in Belgrade and Negotin, respectively.

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On the entrainment in nonprecipitating cumuli — Entrained air provenance     

Ivana Nemešová  Reviewer J. Bednář 《Studia Geophysica et Geodaetica》1985,29(3):300-310

Summary The paper deals with the testing of the cloud top entrainment hypothesis. The method is based on the works by Warner[1–3], Paluch[4] and Telford[5]. The levels at which the entrained air might originate were determined. Several types of successions of entrainment levels were found; in the upper parts of cumuli, entrainment from above the level of observation prevailed.

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mumunma uu ¶rt;a a u. m¶rt; nuam a am aa[1–3], a[4] u ¶rt;a[5]. n¶rt;uu u m¶rt;a ¶rt; nou¶rt;um. u a¶rt; mu muna n¶rt;am m u; a aa na¶rt;am u .

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A steady-state model of a cumulus cloud,describing phase transitions by kinetic equations. I. model pattern     

Ivana Nemešova  Dana Lakomá  Reviewer O. Zikmunda 《Studia Geophysica et Geodaetica》1974,18(3):274-297

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The evaporation of liquid water in describing the dynamic aspects in a model of a convective cloud     

Ivana Nemešová  Reviewer O. Zikmunda 《Studia Geophysica et Geodaetica》1977,21(2):179-184

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On the entrainment in cumuli — A contribution to a case study     

Ivana Nemešová  Reviewer J. Bednář 《Studia Geophysica et Geodaetica》1988,32(1):101-113

Summary The case study presented here is related to the thermodynamic analysis of entrainment and mixing in a shallow cumuls layer. The fair weather situation on 9. 9. 1983, Voves, is characterized by a field of scattered cumuli of the same depths and by a towering isolated cumulus. The clouds were sampled. Two types of analysis were used, the Paluch analysis and saturation point analysis, both of them making use of conserved parameters and a mixing line structure. Both methods gave similar results. For the small cumuli, lateral entrainment prevailed up to the highest penetration level while in the isolated cumulus, cloud top entrainment was the dominant mixing mechanism.

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aam nu, nu¶rt; ¶rt;, n m¶rt;uau aau u u uau a. umau n¶rt; 9. 9. 1983 aamum n a a ¶rt;ua mu u aa u ua a. a aa uau nu nu ama. u nu ¶rt;a muna aaua — aau a u aau nu nu m au; u a unm amu naam u n¶rt; mm uu uau. a m¶rt;a ¶rt;au n¶rt; mam. a a na¶rt;a u ¶rt; a nuu, m a uua a ¶rt;uuu au uau aa u u.

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Climate Change Projections Based on GCM-Simulated Daily Data     

Ivana Nemešová  Jaroslava Kalová  Martin Dubrovský 《Studia Geophysica et Geodaetica》1999,43(2):201-222

Three-dimensional general circulation models (GCMs) are 'state-of-the-art' tools for projecting possible changes in climate. Scenarios constructed for the Czech Republic are based on daily outputs of the ECHAM-GCM in the central European region. Essential findings, derived from validating, procedures are summarized and changes in variables between the control and perturbed experiments are examined. The resulting findings have been used in selecting the most proper methods of generating climate change projections for assessing possible hydrological and agricultural impacts of climate change in selected exposure units. The following weather variables have been studied: Daily extreme temperatures, daily mean temperature, daily sum of global solar radiation, and daily precipitation amounts. Due to some discrepancies revealed, the temperature series for changed climate conditions (2×CO ₂ ) have been created with the help of temperature differences between the control and perturbed runs, and the precipitation series have been derived from an incremental scenario based on an intercomparison of the GCMs' precipitation performance in the region. Solar radiation simulated by the ECHAM was not available and, therefore, it was generated using regression techniques relating monthly means of daily extreme temperatures and global radiation sums. The scenarios published in the paper consist of monthly means of all temperatures, their standard deviations, and monthly means of solar radiation and precipitation amounts. Daily weather series, the necessary input to impact models, are created (i) by the additive or multiplicative modification of observed weather daily series or (ii) by generating synthetic time series with the help of a weather generator whose parameters have been modified in accord with the suggested climate change scenarios.  相似文献   

Degradation of Styrene from Waste Gas Stream by Advanced Oxidation Processes     

Kamila Ko í  Martin Reli  Ivana Troppov  Tom&#x; Prostjovský  Radim ebrk 《洁净——土壤、空气、水》2019,47(8)

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A Relationship Between the Solar Rotation and Activity Analysed by Tracing Sunspot Groups     

Domagoj Ruždjak  Roman Brajša  Davor Sudar  Ivica Skokić  Ivana Poljančić Beljan 《Solar physics》2017,292(12):179

The sunspot position published in the data bases of the Greenwich Photoheliographic Results (GPR), the US Air Force Solar Optical Observing Network and National Oceanic and Atmospheric Administration (USAF/NOAA), and of the Debrecen Photoheliographic Data (DPD) in the period 1874 to 2016 were used to calculate yearly values of the solar differential-rotation parameters \(A\) and \(B\). These differential-rotation parameters were compared with the solar-activity level. We found that the Sun rotates more differentially at the minimum than at the maximum of activity during the epoch 1977?–?2016. An inverse correlation between equatorial rotation and solar activity was found using the recently revised sunspot number. The secular decrease of the equatorial rotation rate that accompanies the increase in activity stopped in the last part of the twentieth century. It was noted that when a significant peak in equatorial rotation velocity is observed during activity minimum, the next maximum is weaker than the previous one.  相似文献