Search

The aim of this study was to determine the concentration of some metals (Ca, Mg, Mn, Fe, Zn, Ni, Cr, Cd) in the soil and species of Tussilago farfara L. and Clematis vitalba L. on the tailings and flotation of the mine DOO "Rudnik". Concentrations in the soil were: Pb and Cu - higher than the maximum allowed, limit and remediation values; Cd, Cr and Ni - higher than the maximum allowed and limit values, and Zn higher than the limit values (according to the regulations of the Republic of Serbia). Better bioaccumulation of all tested metals was shown by T. farfara species, especially leaves for Zn. The results indicate the possible use of aboveground parts of both plant species in the revitalization of tailings by bioaccumulation of tested metals.

A simple ultrahigh-vacuum-compatible Se deposition source is developed. It consists of a resistively heated crucible enveloped by a copper tube that also has provisions for liquid nitrogen cooling. The temperature of the crucible is measured via an Ni/NiCr thermocouple. All feedthroughs are executed through a CF 70 mm OD flange, which enables the Se source to be mounted to different vacuum systems with appropriate flange and sample transport mechanism. The temperature for the onset of the Se evaporation is determined and calibration curves (i.e. Se coverage versus deposition time) for different crucible temperatures above 420 K are measured by Auger electron spectroscopy. The influence of the Se source on the UHV residual gas system is virtually non-existent at operating temperatures below 480 K.

In this study, for the first time, it is shown how the heating of an In–80Sn alloy affects its morphology and surface chemical composition. The study of the initial phases of surface oxidation of the pure In–80Sn alloy at room temperature revealed the formation of a mixture of In 2 O 3 , SnO and SnO 2 oxides with a dominant contribution of In 2 O 3 . The high spatial resolution of the Auger spectrometer enabled us to examine the fine details at various spots on the surface. The results vary from one point of analysis to another. The statistical analysis of a large number of spectra shows clearly an enrichment in the In content in both oxide layer and the clean sample obtained after the oxide layer is removed by heating the sample at 400°C. The thickness of the oxide layer, approximately 3.5 nm, was estimated by AES depth profiling analysis.

A brief review of the high spatial resolution Auger electron spectroscopy (HRAES) and its usage in metallurgy is presented. A combination of HRAES and X-ray photoelectron spectroscopy makes a powerful combination to resolve a large number of problems encountered in metallurgy. Several selected examples of such problems studied in the authors’ laboratory are presented: influence of surface active impurities on the surface properties and structure, chemical composition of nano-scaled inclusions, homogeneity of oxide layers formed by decarburization, chemical composition of inter- and intra-grain surfaces obtained by fracture in vacuum and interfacial study of 19Cr-13Ni austenitic stainless steel after treatment at elevated temperatures., Predočen je kratki pregled Auger-ove elektronske spektroskopije (HREAS) visoke spacijalne resolucije i njene primjene u metalurgiji. Kombinacija HREAS i röntgenske fotoelektronske spektroskopije učinkovita je pri rješavanju velikog broja problema koji se susreću u metalurgiji. Predočeno je nekoliko odabranih primjera takvih problema studiranih u laboratoriju autora: utjecaj površinski aktivnih nečistoća na svojstva i strukturu površine, kemijski sastav “nano-uključaka”, homogenost oksidnih slojeva nastalih odugljičenjem, kemijski sastav površina u zrnu i među zrnima nastalih lomljenjem u vakuumu te međufazna studija 19Cr-13Ni nehrđajućeg austenitnog čelika nakon obrade kod povišenih temperatura.

Edge-defined film-fed grown polycrystalline silicon sheets, grown with one face exposed to oxidizing CO gas added to the inert Ar atmosphere, were studied. Interaction of CO with molten silicon surface during growth produced SiC-like structures in a thin layer on the surface exposed to CO. Infrared spectroscopy results suggest that this layer is constituted of good quality SiC ; however, Raman and x-ray photoelectron spectroscopy showed that it consists of Si1− xCx in the form of small crystallites mixed with C- and O-rich silicon. Journal of Applied Physics is copyrighted by The American Institute of Physics.

Oxygen-, imino-. and/or sulfur-bridged [18]annulenes are studied using the As-index of aromatic stabilization. Theoretical predictions, which indicate that these compounds should differ among themselves in their aromatic properties, correlate nicely with the available experimental findings. Unknown compounds of this class: [18]annulene imino-dioxide and [18]annulene oxide-imino-sulfide are predicted to be aromatic and good candidates for preparation. The same prediction is also reached for 1,10-diaza[18]annulene.

Bifurans (I-III), bipyrroles (IV-VI), bithiophenes (VII-IX), thienylfurans (X-XIII), thienylpyrroles (XIV-XVII), and furylpyrroles (XVIII-XXI) are isomeric biheterocycles formed from two five-membered ring systems (furan, pyrrole, thiophene) linked together by an essential single bond (∼1.47 A).

The most probable conformation of the isomeric thienylpyrroles has been investigated using the HOFFMANN’S variant of the Extended HÜCKEL Theory. Planar syn conformation is predicted slightly more stable than anti for 2,2′-, 2,3′-, and 3,2′-isomers, while the 3,3′-isomer is predicted to have anti conformation slightly more stable than syn. For the two energetically most favourable conformations of each molecule the charge distribution and dipole moment have been calculated using the CNDO/2 method. The relative stability of these compounds has been also discussed.

Dewar's approach to the resonance energy concept is analysed and it is shown that the change in the reference structure is crucial condition for the theory to give an accurate prediction of aromaticity. Thus, the use of simple Huckel theory is justified. Besides, it is shown that part of the correlation energy is contained in the Huckel theory through the parameters α and β.

The recently developed concept of topological resonance energy, TRE, (the optimal non-parametric realization of Dewars-type resonance energy, DRE) is applied to neutral (odd and even) and charged annulenes. Analytical expressions for TRE of neutral annulenes, their mono- and di-cations, and mono- and di-anions are derived. The results obtained are in good agreement with experimental findings for both neutral and charged annulenes.

A simple method based on a topological resonance energy index is proposed for predicting the reactivities of conjugated hydrocarbons. In comparison with other simple methods introduced (e.g., the Kekule structure count method') it embraces both alternant and non-alternant hydrocarbons without additional adjustment of the theory.

Mathematical relations necessary for the calculation of the previously introduced15 topological resonance energy, TRE, are derived. TRE, as defined in ref. 15, was rather inconvenient for numerical calculations. In the present work these computing difficulties are overcome. Acyclic characteristic polynomial pac and acyclic spectrum of a graph are defined and their close relationship to TRE is demonstrated. Hence, the evaluation of pac is the crucial .step in the computation of TRE's. A graphical procedure is described and exemplified for the determination of P"c's both for simple graphs and for graphs with loops and weighted edges.

Ten selected schizophrenic patients and 10 control subjects were assessed in their home language and in a second language for evidence of formal thought disorder. The performance of the schizophrenics was significantly poorer in their home language, while that of control subjects did not differ between the two languages. The results are compatible with Bannister's serial invalidation hypothesis of schizophrenic thought disorder. Of more immediate importance, they indicate that careful attention must be paid to the language used in assessing psychiatric patients in a multilingual society.

Isomeric bicyclic conjugated systems consisting entirely of five-membered heterocycles were studied using a novel aromaticity index named topological resonance energy (TRE). TRE has correctly predicted the aromatic behaviour of all the groups of isomers studied. (These isomers called positional isomers because they formally differ only by the position of a-bivalent heteroatoms) may be classified into a particular group according their annelation mode, which closely parallels TRE predictions and experimental findings.

Annulenes were studied using the concept of aromatic stabilization. A simple expression is presented for the calculation of aromatic stabilization of annulenes. The index of aromatic stabilization differentiates correctly between the [4n + 2] - and [4n] -annulenes. The analysis of the approach of Kruszewski and Krygowski shows that their KK index differs only by a constant from the value of aromatic stabilization of a particular annulene. Similarly, the relation between REPE values of Hess and Schaad and indices of aromatic stabilization is discussed.