Earlier investigations of the inuence of geomagnetic activity on radio wave absorption were based on storm selection criterion: SKp ³ 30. This criterion lumped together weak, moderate, and strong storms, and favouring weak and moderate storms made it impossible for the investigations to detect any change in equatorial radio wave absorption following geomagnetic storms. Presently, the effect of geomagnetic storms on equatorial radio wave absorption has been investigated using severe storms (Ap ? 54) and HF absorption data obtained at 4.87 MHz at 1000 hours LT at Lagos (3. 40oE, 6. 55oN). The absorption data were measured using radio waves reected from the F region, and the transmitter (Radio Cotonou) is located at Cotonou (2.43oE, 6.35oN). The present results obtained using the superposed epoch method show that HF absorption in the equatorial ionosphere increases after severe geomagnetic activity.
HF absorption enhancements following major geomagnetic storms are analysed, using the superposed epoch method, to examine the geomagnetic latitude limit of the after-effect phenomenon. The absorption data were obtained from one double hop and two single hop A3 transmission paths with ionospheric points at Fgeomag = 3:54oN and ~6. 40oN (15. 40 MHz), Fgeomag ~ 9N (4. 87 MHz), and Fgeomag ~ 11oN (6. 09 MHz) respectively. Presently, the results have shown that enhancement in absorption following major storms could be traced to the low latitude of 3. 54oN.
The CT technique is unique because it provides a non-destructive evaluation of sedimentary rocks. The absorption of X-radiation, emitted by a high-voltage generator, depends on the bulk density and atomic weight of the substance. The lower the density of the material, the more transparent it is to X-rays. If the emitted energy is constant, the absorption depends only on the density of the substance, which is represented by different Hounsfield Units. In case study No. 1, a pelitic core sample of an ox-bow lake environment was analyzed. The mathematical-statistical estimates and significant time-series model (ARIMA) proved that the data coming from the CT images show the presence of micro-cycles. The applied method proved the influence of seasonal floods on local sedimentation. In case study No. 2, the data represent a younger and an older Bouma sequence. The macroscopic study suggests that there are two C units in the core, because an erosional surface is clearly identifiable between the older and the younger units. This case study shows the necessity of precise sedimentological knowledge in addition to that of mathematical-statistical methods and software, and that an accurate macroscopic study is essential and never replaceable. Also, it should be kept in mind that it is often reasonable to replace the conventional statistical conception with a geostatistical approach. The aim of this study was to demonstrate a “non-traditional” strategy in sedimentology and the interpretation thereof.
Three types of porous limestone from Sóskút quarry and two limestone types obtained directly from Matthias Church of Budapest (both in Hungary) were used to test the performance of five stone consolidants. The quarry specimens were treated under laboratory conditions by saturation. Three types of silicic acid ester, an aliphatic uretan resin and a polymethyl methacrylate were applied to the stone. Physical parameters such as density, porosity, ultrasonic sound velocity and Duroscope rebound value were measured on untreated and treated samples. The absorption rate of different consolidants was also detected. The physical properties of untreated and treated specimens were compared in order to analyze the performance of the consolidants. Duroscope tests have shown that after consolidation there is an increase in surface strength.
An "unknown Ni-Al hydrosilicate" was found in the karstic nickel deposits in the localities Ba and Takovo in Serbia, and Aghios Ioannis in Greece. It occurs in fine-grained bluish-green and green aggregates with takovite and hydrated halloysite. It is an epigenetic product in the karstic nickel deposit. X-ray powder diffraction (XRPD) data are indexed with a monoclinic unit cell, a = 8.524 (4), b = 7.490 (3), c = 24.214 (6) Å, b = 104.55 (6)°, V = 1545.9 Å3. The thermal study has shown a characteristic dehydroxylation effect at 450 °C, which distinguishes this mineral from takovite and halloysite. The infra-red technique is very sensitive for the detection of the "unknown Ni-Al hydrosilicate": an absorption band between 1250 cm-1 and 1270 cm-1 is very characteristic for this mineral. From chemical analyses of the admixture of this mineral and hydrated halloysite in different proportions from the Aghios Ioannis deposit in Greece, after removal of impurities, the calculated formula is close to Ni2.00 Al2.00 (Si1.93 Al0.07) on the basis of 12 (O,OH).
Authors:Zsófia Pálos, István János Kovács, Dávid Karátson, Tamás Biró, Judit Sándorné Kovács, Éva Bertalan, Anikó Besnyi, György Falus, Tamás Fancsik, Martina Tribus, László Előd Aradi, Csaba Szabó, and Viktor Wesztergom
; SIMS: secondary ion mass spectrometry; XANES: X-ray absorption near-edge spectroscopy; SHRIMP-SI: stable isotope sensitive high-resolution, ion microprobe; SC-XRD: single crystal X-ray diffraction