Correlation Between Composition and Properties of Amorphous Bismuth-doped As2S3

U ovom radu prikazani su rezultati ispitivanja termičkih, mehaničkih, električnih i optičkih karakteristika kvazibinarnih halkogenida iz sistema Bi-As2S3. Na osnovu termičkih merenja analizirana je kinetika kristalizacionih i predkristalizacionih procesa i utvrđen je mehanizam dekompozicije za različite sastave dobijenih stakala. Primenom impedansne spektroskopije kvantitativno su ocenjeni doprinosi relaksacionih procesa na pojedinim temperaturama u ukupnoj polaraziciji za stakla sa 5 i 7 at.% Bi. Na osnovu merenja Raman spektroskopije identifikovane su nastale strukturne jedinice i konstatovana pojava nanofazne separacije u staklima sa 1.5 i 3 at.% Bi. Mehanička merenja ispitivanih halkogenida različitog sastava ukazala su na povećanje Vickers-ove tvrdoće sa povećanjem udela primesnih atoma. Na osnovu procenjene vrednosti modula elastičnosti ustanovljeno je da uzorak sa 5 at.% Bi odlikuje najgušće atomsko pakovanje. Merenja električnih karakteristika u jednosmernom režimu (DC) pokazala su da je udeo lokalizovanih stanja u ukupnom mehanizmu provođenja značajan samo za manje koncentracije primesnih atoma, a da za veće koncentracije dominantan faktor postaju preskoci između delokalizovanih stanja. Skok u provodljivosti za nekoliko redova veličine kod sastava sa složenijom strukturom protumačen je kao posledica fazne separacije. Rezultati  ACmerenja dobijeni za sastav sa 5 at.% Bi ukazali su da je u mernom frekventnom intervalu i dalje dominantan mehanizam termičke aktivacije nosilaca naelektrisanja. Kod sastava sa maksimalnim sadržajem Bi uočena je promena provodljivosti u funkciji frekvencije na svim temperaturama, a dobijeni rezultati su u skladu sa postavkama modela korelisanih preskoka barijere (CHB model).This paper presents the results of investigation ofthermal, mechanical, electrical and optical propertiesof quasibinar chalcogenides from the system Bi-As2S3. Kinetics analysis of softening and crystallizationprocesses was done on the basis of thermalmeasurements, as well the analysis of decompositionmechanism for different compositions of obtainedglasses. The application of impedance spectroscopy enabled quantitative description of relaxation process contributions at selected temperatures in the overallpolarization for the samples with 5 and 7 at.% Bi. Based on measurements of Raman spectroscopy identification of structural units in the investigated chalcogenides was made, as well as the appearance of nano-scale phase separation in the glasses with 1.5 and 3 at.% Bi. Mechanical measurements pointed to the increase of the Vickers hardness with increase of doping atoms content.  Based on the estimated value of the modulus of elasticity it was found that the sample  with 5 at.% Bi is characterized by the densest atomic arrangement. Measurements of the electrical properties in dc regime (DC) pointed out that the share of localized states in the whole mechanism of conduction is significant only for the smaller concentrations of doping atoms. For the samples with higher concentrations dominant  factor in conductivity are transitions between delocalized states. The jump in conductivity by few orders of magnitude, noticed for the compound with heterogeneous structure was interpreted as a consequence of micro-scale phase  separation. Results of  ACmeasurements for the  composition with 5 at.% Bi showed that the mechanism of thermal activation of charge carriers is still dominant in the measured frequency range. For   the composition with the maximum content of Bi changes in conductivity versus frequency were observed at all temperatures, and the results were interpreted in accordance with the model of correlated hopping over the barrier (CHB)

Investigation on antibacterial synergism of Origanum vulgare and Thymus vulgaris essential oils

Essential oils are well known as strong antimicrobial agents of plant origin. In spite of this, the antimicrobial synergism of essential oils isolated from different plant species is poorly investigated. The following study examines the synergism of the essential oils of Origanum vulgare L. and Thymus vulgaris L against pathogenic bacteria, Staphylococcus aureus and Salmonella typhimurium. First, the antibacterial effect of the oils was tested, and the minimal inhibitory concentrations (MIC) of both oils were determined using the microdilution method. To test whether the oils act synergistically, every possible combination of essential oil concentrations was used in a dynamic checkerboard method. The results indicated that the oils indeed acted synergistically with fractional inhibitory concentration indexes of 0.45 and 0.50. [Projekat Ministarstva nauke Republike Srbije, br. 173032

Chemical analysis and antimicrobial activities of the essential oils of Satureja thymbra L. and Thymbra spicata L. and their main components

This work covers the chemical composition and antimicrobial activities of the essential oils isolated from Satureja thymbra and Thymbra spicata analyzed using GC/MS. The main components of S. thymbra oil were thymol (33.8 %), γ-terpinene (30.8 %) and p-cymene (11.8 %). The main components in T. spicata oil were carvacrol (74.5 %) and γ-terpinene (11.2 %). The oils and their main components, thymol and carvacrol, were assayed by applying the microdilution method for antibacterial and antifungal activity against food poisoning, plant, animal and human pathogenic microorganisms. The oil of T. spicata and carvacrol showed the highest antimicrobial activity.Projekat ministarstva br. 17303

Antimicrobial activity of aqueous extract of Laetiporus sulphureus (Bull.: Fr.) Murill

Wood-rotting basidiomycete, Laetiporus sulphureus (Bull.: Fr.) Murill., also known as chicken of the woods, is known for its nutritional value. In this study, aqueous extract obtained from L. sulphureus was investigated for its antimicrobial properties using microdilution in vitro assay. Plant, animal and human pathogens, as well as food spoilage agents, were tested. Aqueous extract obtained from L. sulphureus showed strong activity against the tested microorganisms in a dose dependent manner. Considering that there is a constant emerging of pathogen resistance to the known synthetic agents, there is an undeniable need for new therapeutical drugs and preservatives in food industry. Thus, these results that indicate activity of natural products may be of practical use.Gljiva mrke truleži, Laetiporus sulphureus (Bull.: Fr) Murill., poznata i kao šumsko pile, već je poznata po svojoj nutritivnoj vrednosti. U ovoj studiji ispitivana je antimikrobna sposobnost vodenog ekstrakta L. sulphureus, mikrodilucionom in vitro metodom. Biljni, životinjski i humani patogeni, kao i prouzrokovači kvarenja hrane su testirani. Vodeni ekstrakt dobijen od L. sulphureus pokazao je snažnu aktivnost na testirane mikroorganizme uz doznu zavisnost. S obzirom da postoji konstantni porast rezistentnosti patogena na poznate sintetičke agense, potreba za novim terapeutskim lekovima i konzervansima u prehrambenoj industriji je neophodnost. Stoga, rezultati koji ukazuju na aktivnost prirodnih produkata mogu biti od velikog praktičnog značaja.Projekat ministarstva br. 14304

Investigation on antibacterial synergism of Origanum vulgare and Thymus vulgaris essential oils

Essential oils are well known as strong antimicrobial agents of plant origin. In spite of this, the antimicrobial synergism of essential oils isolated from different plant species is poorly investigated. The following study examines the synergism of the essential oils of Origanum vulgare L. and Thymus vulgaris L against pathogenic bacteria, Staphylococcus aureus and Salmonella typhimurium. First, the antibacterial effect of the oils was tested, and the minimal inhibitory concentrations (MIC) of both oils were determined using the microdilution method. To test whether the oils act synergistically, every possible combination of essential oil concentrations was used in a dynamic checkerboard method. The results indicated that the oils indeed acted synergistically with fractional inhibitory concentration indexes of 0.45 and 0.50.Projekat ministarstva br. 17303

Multiply charged ions from solid substances with the mVINIS Ion Source

We have used the well known metal-ions-from-volatile-compounds (MIVOC) method at the mVINIS Ion Source to produce the multiply charged ion beams form solid substances. Based on this method the very intense and stable multiply charged ion beams of several solid substances having the high melting points were extracted. The ion yields and the spectra of multiply charged ion beams obtained from solid materials like Fe and Hf will be presented. We have utilized the multiply charged ion beams from solid substances to irradiate the polymers, fullerenes and glassy carbon at the low energy channel for modification of materials.13th International Conference on Physics of Highly Charged Ions, Aug 28-Sep 01, 2006, Queens Univ, Belfast, Irelan

Effects of the Ar ions pre-amorphization of Si substrateon interface mixing of Fe/Si bilayers

Ion beam mixing of Fe/Si bilayers, induced by 100 keV (40)Arions at room temperature was investigated. Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for structural characterization. The main focus of this study was on the influence of the substrate structure on interface mixing. The influence of the substrate structure is due to the two classes of irradiated bilayers, Fe thin films deposited on crystalline or pre-amorphized Si substrates. An about 76% higher efficiency of atomic transport across the pre-amorphized Fe/a-Si interface as compared to that of Fe/c-Si bilayers was observed

Structural deformation in Hf2Ni observed by TDPAC method

The electric quadrupole interaction in Hf2Ni was measured at 181Ta probe using the time-differential perturbed angular correlation method (TDPAC) in the temperature range 78 to 1314 K. Analysis of the obtained spectra revealed the presence of a single nuclear quadrupole interaction (NQI) and its linear descending dependence with increasing temperature. In the region 1134 to 1314 K, the presence of structural deformation is evident from the coincidence spectra.YUCOMAT 2007 : 9th Annual Conference YUCOMAT 2007 : Programme and the book of abstracts; September 10-14, 2007; Herceg Novi, Montenegr

Hyperfine interactions at 181Ta solute in ferromagnetic Hf-Ni alloys with low concentration of Hf atoms

We have measured hyperfine interactions of 181Ta probe in the polycrystalline 0.2at.%Hf-Ni, 2at.%Hf-Ni and 5at.%Hf-Ni alloys, by the time differential perturbed angular correlation (TDPAC) method at room temperature (RT). The hyperfine magnetic field (Hhf) in 0.2at.%Hf-Ni alloy at the 181Ta probe is 8.66(1)T, where the small atomic concentrations of Hf atoms mainly substitute on Ni host lattice sites. Three hyperfine interactions were detected in two other alloys. In the 2at.%Hf-Ni alloy, we found existence of Larmor precession frequency ωL (1)=536(2)Mrad/s at the 181Ta probe surrounded by Ni atoms and the second electric quadrupole interaction (EQI) ωQ (2)=2.20(2)Mrad/s at the 181Ta probe in new formed HfNi5 intermetallic phase. The third EQI ωQ (3)=137.4(1)Mrad/s corresponds to the small amount of monoclinic HfO2 phase contamination at T<900K. In the 5at%Hf-Ni alloy, magnetic dipole interaction (MDI) at the 181Ta probe is ωL (1)=536(6)Mrad/s, while the second EQI at the site of the same probe in HfNi5 is ωQ (2)=2.24(2)Mrad/s. The presence of ωQ (3)=128(1)Mrad/s at the 181Ta probe originating from HfO2 contamination is in good accordance with earlier published results for this phase.52. konferencija ETRAN-a : Jun 8-12, Palić, 2008