Tania Ristoiu
Technical University of Cluj-Napoca
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Featured researches published by Tania Ristoiu.
Materials Science and Engineering B-advanced Functional Solid-state Materials | 2000
E. Culea; Tania Ristoiu; I. Bratu; Delia Ristoiu
Glasses of the xDy2O3O1ˇ xUNa2B4O7 system with 0:016 x6 0:15 were studied using IR spectroscopy, density and magnetic susceptibility measurements. IR spectroscopic and density data show that the dysprosium ions play a network modifier role in the studied glasses. Magnetic susceptibility data show a mictomagnetic type behaviour due to the presence of both isolated and exchange coupled Dy 3a ions. ” 2000 Published by Elsevier Science B.V. All rights reserved.
Materials Science and Engineering B-advanced Functional Solid-state Materials | 1999
E. Culea; Tania Ristoiu; I. Bratu
Abstract The x Ho 2 O 3 –(1− x )Na 2 B 4 O 7 glass system (0≤ x ≤0.20) was studied by magnetic susceptibility, density and IR spectroscopic measurements. Magnetic susceptibility data suggest the presence of Ho 3+ ions both as isolated and exchange coupled species. IR and density measurements give evidence of the network modifier role played by the holmium ions in these glasses.
Materials Letters | 1999
Tania Ristoiu; E. Culea; I. Bratu
Abstract Glasses of the xGd2O3·(1−x)Na2B4O7 system (0≤x≤0.20) were studied by electron paramagnetic resonance (EPR), magnetic susceptibility, density and IR spectroscopic measurements. EPR and magnetic susceptibility data show the presence of small antiferromagnetic interactions between the Gd3+ ions. IR and density measurements show that an important decrease of the boroxol structural groups occurs for x≥0.15.
Journal of Non-crystalline Solids | 2001
Tania Ristoiu; E. Culea
Abstract Glasses of the x Eu 2 O 3 (1− x )Na 2 B 4 O 7 system with 0.05⩽ x ⩽0.30 were studied by magnetization measurements. Their magnetic behaviour is due to the presence of europium ions in both 2+ and 3+ valence states. Low-temperature (4 K) magnetization data showed the presence of a magnetically ordered phase due to the Eu 2+ ions and permitted an estimation of their amount.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2013
M. Rada; R. Chelcea; S. Rada; L. Rus; N. Dura; Tania Ristoiu; T. Rusu; E. Culea
Glasses from xCuO⋅(100-x)[7GeO(2)⋅3PbO(2)⋅0.05Al(2)O(3)] system where x=0, 1, 5, 10, 20 and 30 mol% CuO were studied by FT-IR, UV-VIS and ESR spectroscopy in order to obtain information about the structural correlations and the relationship between structure and optical properties in these materials. The analyses of these IR spectra reveal that the accommodation of the network with the excess of oxygen ions is possible by the depolymerization of the germanate network in shorter chains, especially ortho- and/or pyrogermanate structural units. UV-VIS absorption spectrum of the sample with x=1% CuO begins with a rising absorption band situated at about 250 nm. This band can be assigned to the GeOGe wrong bonds such as the Ge(+2) centers. Optical study is performed to calculate the refractive index and optical band gap using UV-VIS spectra in the wavelength range 250-1,000 nm. The increase in optical band is explained on the basis of the average bond energy of the system and the number of non-bridging oxygen ions. ESR spectra of CuO substituted samples are characterized by broad peaks probably because of the formation of Cu(+2)-Ge(+2) exchange pairs which are weakly coupled though the oxygen atom.
Vacuum | 1998
Dumitru Ristoiu; C Cosma; A Voros; Tania Ristoiu
Abstract A simple flow cell membrane inlet for Volatile Organic Compounds (VOCs) was constructed and tested in our laboratory. The purpose of this study was to evaluate the performances of the Membrane Inlet-Quadrupole Mass Spectrometry technique for on-line analysis and continuous monitoring of various compounds from environmental samples. The method showed a good linearity, precision, and reproductibility for some frequently used chemical solvents such as benzene, toluene, acetone, methanol, and ethanol. The method permits the determination of concentrations down to 0.04–4 mg m −3 , depending on the compounds.
Modern Physics Letters B | 2006
Lidia Pop; Tania Ristoiu; N. Dempsey; Monica Culea; E. Culea
Glasses of the xEu2O3(1-x)[3Bi2O3PbO] system with x=0–0.25 were prepared and studied using low-temperature magnetization measurements. The obtained data suggest the presence of both Eu3+ and Eu2+ ions in the host glass matrix. The determined fraction of the Eu2+ ions/total number of europium ions was very small (2.1–3.4%). Magnetization data show that the europium ions exert superexchange interactions and show an important clustering tendency.
SIXTH INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION | 2007
L. Ciontea; Tania Ristoiu; R.‐C. Suciu; T. Petrisor
A solution processing technique was used to deposit an epitaxial Y2O3 film on (001)[100] cube textured Ni tapes for YBa2Cu3Ox (YBCO) coated conductors manufacturing. The cube texture was developed in Ni by a conventional thermo-mechanical process. A precursor solution of yttrium 2-methoxyethoxide in 2-methoxyethanol was spin-coated on the Ni substrate. The as-deposited amorphous film was thermally treated at 1100 deg. C in a flowing Ar+4%H2 gas mixture. The {theta}-2{theta} X-ray spectra revealed predominantly (001) reflections, indicating a high degree of out-of-plane orientation. Pole figures for the (222) Y2O3 reflections demonstrate a single in-plane texture. The out-of-plane and in-plane epitaxial relationship is [400]Y2O3//[200] Ni and [110]Y2O3//[100] Ni, respectively. The full-width-half-maximum (FWHM) of the {omega}-scans and {phi}-scans is 6 deg. and 11 deg. , respectively.
Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies V | 2010
Melinda Haydee Kovacs; Dumitru Ristoiu; Tania Ristoiu
Biomonitoring studies for estimation population health surveillance and exposure risk assessment of different chemical contaminants such as chlorinated compounds or polycyclic aromatic hydrocarbon (PAH) compounds has become an important task especially after the Stockholm Convention. If before the toxicological evaluation of humans were done using invasive methods like surgery or pricking, today many scientists tried to elaborate non-invasive analytical methods without disparage the final results. During the last years studies it was observed a relative higher pollution with organochlorine and polycyclic aromatic hydrocarbon compounds in surrounding regions of Dej, Transylvania. These past studies shown that pollution with chlorinated compounds as chlorinated solvents are attributed to the industrial activities from this region. The levels in soil and river water of these compounds were: ≈ 20 - 60 μg·kg-1 and ≈ 15 - 45 μg·L-1, respectively. In case of PAHs the following results were obtained for soil and river water: for two ring specie was between ≈ 26 - 35 μg·kg-1 and ≈ 21 - 30 μg·L-1, respectively; for three ring species was 15 - 35 μg·kg-1 and ≈ 10 - 24 μg·L-1, respectively; and in case of four ring species was between 10 - 20 μg·kg-1 and ≈ 3 - 15 μg·L-1, respectively. These results carry on concern regarding the bioaccumulation of these pollutants by humans through food web chain. In order to establish the uptake level of these compounds by humans, home grown animal hair as pig and cow were analyzed through SIM-GC-MS mode and ECD-FID-GC. The presence of chlorinated solvents detected in pig and cows hair were as follows: compounds from chloromethane family ≈ 5 - 10 ng·kg-1 dry weight; compounds from chloroethane family ≈ 7 - 34 ng·kg-1 dry weight for pig hair, and ≈ 12 - 17 ng·kg-1 dry weight for compounds from chloromethane family and 14 - 48 ng·kg-1 dry weight for cow hair. Difference between accumulation levels of PAH metabolites were observed also between cow and pig hair samples.
Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies IV | 2009
Dumitru Ristoiu; Melinda Haydee; Tania Ristoiu
Exposures to disinfection by-products (DBPs) in residential drinking water occur through multiple routes and vary across the population because of differences in the amount and ways people use water. Municipal water in the Romania is disinfected, with chlorine being the most common disinfectant agent. Disinfection of water, in additional to having the benefit of destroying microbes that can transmit diseases, has the drawback of producing a series of compounds known as disinfection by-products (DBPs). Chlorination produces many compounds containing chlorine and/or bromine, some of which have been shown to be carcinogenic, mutagenic, and/or teratogenic in animal studies. The most abundant class of DBPs that result from chlorination of drinking water are trihalomethanes (THMs) - chloroform (CHCl3), dichlorobromomethane (CHCl2Br), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3). The most predominant THM species was CHCl3 and it highest concentration was 85∙106 ng/m3. The others THMs compounds concentration were lower, between 65∙104 ng/m3 and 12∙106 ng/m3. THMs compounds were analyzed on gas chromatography coupled with mass spectrometer detector (GC-MS) and head space technique (HS) was used for all analysis.