Authors:M. Reddy, A. Damodaran, J. Mathur, M. Murali, and R. Iyer
Mixed-ligand chelate extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am into xylene with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and dihexyl-N,N-diethylcarbamoylmethylphosphonate (CMP) has been studied by tracertechniques. These trivalent metal ions are found to be extracted from 0.01 mol/dm3 chloroacetate buffer solutions as M(PMBP)3·HPMBP type self adducts with HPMBP alone and in the presence of CMP as M(PMBP)3·CMP (where M=La, Eu, Lu and Am) into the organic phase. The equilibrium constants of the above species are deduced by non-linear regression analysis. The synergistic constants of trivalent lanthanides do not increase monotonically with atomic number but have a maximum at Eu and that of Am was found to lie between that of La and Eu.
The crustal and uppermost mantle structure beneath the Mátra Mountains has been investigated by means of the inversion of teleseismic P-wave receiver functions. Earthquakes recorded at the PSZ station in the period 1995-2000 with epicentral distances of between 20° and 100° and with magnitudes greater than 5.5 have been selected for analysis if their signal-to-noise ratio was sufficiently high. Source equalisation has been carried out to gain the radial and tangential receiver functions. The traces from similar backazimuths and distances were stacked to improve the data quality. The inversion of teleseismic waves coming from the north-east and the west shows that in the upper part of the crust the S-wave velocity has strong positive gradient, the middle crust exhibit almost uniform velocities, while in the lower crust and uppermost mantle the velocity increases monotonically. Velocity profiles for the eastern backazimuths are similar to the previous ones in the case of the upper and middle crust and uppermost mantle, however in the lower crust a low-velocity zone can be observed. The properties of polarity distribution of tangential receiver functions can be associated with WNW-dipping lower crustal interfaces.
A copper, zinc and aluminium mixed oxides sample having the nominal composition 0.25 CuO/0.03 ZnO/Al2O3 was prepared by impregnating Al(OH)3 with copper and zinc nitrate solutions, drying at 100 °C then heating in air at 600 °C. The obtained solid was exposed to different doses of -rays (20–160 Mrad). The surface characteristics namelySBETVP andr of different treated adsorbents were determined from N2 adsorption isothems measured at –196 °C. The catalytic activity of various irradiated solids was determined by following up the kinetics of CO-oxidation by O2 at 150–200 °C. The results showed that the doses up to 80 Mrad resulted in no significant change in theSBET but increased slightly theVP (20%) of the treated adsorbents. The irradiation at 160 Mrad caused an increase of 20% in theSBET of the irradiated solid sample. The catalytic activity increased progressively by increasing the dose, a dose of 160 Mrad brought about an increase of 140% in the catalyst's activity. The apparent activation energy of the catalytic reaction decreased monotonically by increasing the absorbed dose of -rays which was attributed to a parallel induced decrease in the value of pre-exponential term of the Arrhenius equation. The observed increase in the catalytic activity due to -irradiation has been interpreted as a result of increasing the concentration of catalytically-active sites contributing in chemisorption and catalysis of CO-oxidation via a possible fragmentation of CuO crystallites.
To avoid the problems associated with the Euclidean distance for the calculation of plot-to-plot dissimilarity, a variety of alternative measures have been proposed. Among them, the chord and the Hellinger distances are both obtained by first transforming separately the species abundances in each plot vector and then by calculating the Euclidean distance on the chord-transformed or the Hellinger-transformed data. However, although both measures are routinely used by ecologists as substitutes for the Euclidean distance, they have very different properties. In this paper, using a modified version of Dalton's principle of transfers, I will show that, unlike the Euclidean distance, the chord and the Hellinger distances are not monotonic to changes in absolute abundances. Therefore, they are not interchangeable with the Euclidean distance. The moral of this story is that although dissimilarity may appear an intuitively simple concept, the properties of even the best-known indices are not fully understood. Therefore, a clear understanding of old and new coefficients is needed to evaluate their ability to highlight relevant aspects of compositional dissimilarity among plots.
Authors:R. De Lisi, G. Lazzara, S. Milioto, and N. Muratore
Macromolecule/laponite nanomaterials were
studied by DSC and X-ray diffraction techniques. The matrices are poly(ethylene)
glycols at various molecular masses and poly(ethylene oxides)-poly(propylene
oxides)-poly(ethylene oxides) tri-block copolymers. The latter were tuned
by modulating the molecular masses, at constant hydrophilic/hydrophobic ratio,
and the hydrophilicity. For all the investigated systems, the enthalpy of
is nearly constant up to a given composition thereafter it increases monotonically
reaching the value of the pure macromolecule. We proposed a model to interpret
the DSC data.
Briefly, it was invoked a mechanism of interaction
following which some segments of the adsorbed macromolecule are anchored to
the laponite (RD) particles and the remaining segments are radiating away
from the surface. The portion of the macromolecule in contact with RD does
not contribute to ΔHm
whereas that radiating away from the clay does. Once that the RD surface is
saturated, the excess of the macromolecule behaves like the pure one. The
proposed model allowed to compute successfully the ΔHm
values. The X-ray diffraction experiments ruled out the polymer intercalation
between the silicate sheets.
Authors:Cristian Vulcu, Aurel Stratan, and Dan Dubina
Dual-steel structural systems, in which mild carbon steel is used in dissipative members while high strength steel is used in non-dissipative ‘elastic’ members, can be very reliable and cost efficient. Because present seismic design codes do not cover this specific configuration, a research project started with the aim to investigate and evaluate the seismic performance of dual-steel building frames. The frames are considered to be moment resisting frames, dual concentrically braced frames and dual eccentrically braced frames. The paper makes a short description of the research project and the experimental program to be performed at the ‘Politehnica’ University of Timisoara.A number of numerical simulations have been performed for the beam-to-column joints that will be tested with the aim to assess their behavior under monotonic as well as cyclic loading. The material model used in the numerical simulations was calibrated based on the results from tensile tests. The assumptions considered in the modeling of the specimens, the loading procedure, as well as the results from the numerical analysis are finally presented.
The Hg-, Cd- and UO2-targets bombarded by protons have been treated using the sublimation and evaporation techniques. The Hg and Cd nuclei have
been separated from non-isotopic products by distillation in the hydrogen stream. The separation of the groups of Re, Os,
Ir, Mo, Tc and Ru oxides has been carried out in the air stream. No monotonic temperature dependence of the Tl, Ru, Mo, Tc,
Te, Pb and Po release has been observed in the oxidation of the UO2-ceramics in the air stream. The values of (−ΔH
) of volatile products adsorbed on quartz have been determined from the chromatographic data. The relation between the adsorption
) and the standard sublimation heat (ΔH
subl.) has been found to be linear, i.e. −ΔH
(subl.). As an example of the thermochromatographic generator of isotopes, the separation of99Mo to99mTc has been investigated.