The correlation of processes of crystallization and changes of free electron density amorphous alloy powder Co80Ni20

Great attention is being given today to investigations on the capabilities and structural changes of amorphous and nanocrystal materials. Structural changes of the amorphous cobalt and nickel alloy powder obtained by electrochemical deposition were investigated in this paper. The crystallization process, as determined by the DSC method, occurred in two steps. The temperature dependence of electrical resistively and magnetic susceptibility in isothermal and non-isothermal conditions within the temperature range of room temperature to 700ºC was determined for the powder samples pressed under pressure of 800 MPa. The X-ray structural examinations results correlate with those of the DSC analysis and the electrical resistively measuring

A study of the low-lying singlet and triplet electronic states of chlorophyll A and B

Chlorophylls have been extensively investigated both experimentally and theoretically owing to the fact that they are essential for photosynthesis. We have studied two forms of chlorophyll, chlorophyll a and chlorophyll b, by means of density functional theory. Optimization of S0, S1 and T1 states was performed with the B3-LYP functional. The computed fluorescence lifetimes show good agreement with the available experimental data. The electronic adiabatic energies of S1 and T1 states are 2.09/2.12 and 1.19/1.29 eV for chlorophyll a and chlorophyll b respectively. We discussed the implications of this results on the triplet formation. Also, the calculated vertical ionization potentials shows good agreement with the experimental results. [Projekat Ministarstva nauke Reoublike Srbije, br. 172040

Isothermal sintering of BZT ceramics

Starting mixtures of BaCO3 •ZnO and Ti02 were mechanically activated for 0,5, 10,20.40 and 80 minutes in a planetary ball mill. The powders obtained were sintered isothermally to temperatures between 1000 and 1300 °C. The phase composition of powders and sintered samples were followed by X-ray analyses. Also, the changes in microstructures were detected using SEM

A phenomenological analysis of sintering kinetics from the viewpoint of activated volume

The sintering kinetics of real systems has been viewed as a process of transport of activated volume. Activated volume is a parameter that can be used to describe mass transport during the sintering process. It defines the movement of point defects and dislocations during the sintering process. A phenomenological equation has been defined using this parameter, which can be applied to analyze kinetics of the sintering process. It has been applied to analyze the sintering process of several disperse systems. Values obtained for parameters of the equation have also been analyzed

Modification of the structural and optical properties of commercial ZnO powder by mechanical activation

Mechanical activation was used as a method for modification of the structural and optical properties of commercial ZnO powder. For this purpose zinc oxide powder was mechanically treated by grinding in a high-energy vibro-mill in a continual regime in air up to 300 minutes. Starting and modified ZnO samples were characterized using XRD, BET and TEM measurements. Optical properties of these samples were investigated by Raman and photoluminescence (PL) spectroscopy. The color of commercial ZnO powder was white while mechanically activated ZnO powder was dark yellow, indicating the presence of nonstoichiometry. In the Raman spectra of non-activated sample Raman modes of bulk ZnO were observed, while the spectra of modified samples point out structural and stoichiometric changes. The PL spectra of modified samples excited by 325 and 442 nm lines of a He-Cd laser show great difference with respect to the spectra of the original sample. This study confirms that change in the defect structure of the ZnO crystal lattice introduced by mechanical activation affects the optical properties of this material

Radiographic examination of apical root resorption and alveolar bone loss after active phase of orthodontic therapy of malocclusions with fixed orthodontic appliances

Uvod i cilj. U toku aktivne faze terapije malokluzija fiksnim ortodontskim aparatima sile ortodontskih lukova se prenose na koren zuba i okolnu alveolarnu kost i na taj način dovode do pomeranja zuba. Cilj naše studije je da radiografskim metodama ortopantomografije i kompjuterizovane tomografije odredimo da li tokom delovanja ortodontskih sila na zube dolazi do resorpcije cementa korena zuba i okolne alveolarne kosti. Pacijenti i metodi. U periodu od marta 2008. do maja 2012. godine u studiju je uključeno 85 pacijenata (27 muškog i 58 ženskog pola) uzrasta od 10 do 22 godine kod kojih je sprovedeno lečenje malokluzije gornjim i/ili donjim fiksnim ortodontskim aparatom. Kod svih ispitanika ortopantomogram je snimljen neposredno pre početka i najviše mesec dana nakon završetka terapije fiksnim ortodontskim aparatima, a kod 35 pacijenata istovremeno je sniman i kompjuterizovani tomogram dva ili tri susedna zuba. Dužina korena zuba u obe vilice određivana je na ortopantomogramu kod svih ispitanika samo na zubima sa završenim rastom korena. Merenjem su obuhvaćeni centralni i lateralni sekutići, očnjaci, prvi i drugi premolari i prvi stalni molari. Na početnom i završnom ortopantomogramu i kompjuterizovanom tomogramu dužina korena zuba je merena kao rastojanje između cementno-gleđne granice i vrha korena zuba. Dužina korena zuba merena je direktno na ortopantomogramu lenjirom sa milimetarskom podelom do najbližeg podeoka od 0.5 mm sa mezijalne i distalne strane svih ispitivanih zuba, a na kompjuterizovanim tomogramima pomoću i-Dixel i Syngo Fastview softvera. Visina alveolarne kosti na početnim i završnim radiografijama određivana je u predelu svih zuba obe vilice kod kojih je izvršeno i merenje dužine njihovih korenova. Visina alveolarne kosti određuje se kao rastojanje između apeksa korena zuba i najkoronarnijeg dela alveolarne kosti sa normalnom debljinom periodontalnog prostora od 0.5 mm. Poređenjem vrednosti dužine korena zuba i visine alveolarne kosti dobijenih merenjem na početnim i završnim radiografijama dobija se iznos resorpcije korena zuba i alveolarne kosti. Na kompjuterizovanim tomogramima određivali smo i debljinu kortikalne alveolarne kosti i širinu periodontalnog prostora oko ispitivanih zuba...Introduction and aim. During the active phase of orthodontic therapy of malocclusions orthodontic forces are transmitted to tooth root and adjacent alveolar bone producing tooth movement. The aim of our study is to determine whether the orthodontic forces induce resorption of root cementum and alveolar bone using orthopantomography and computerized tomography. Patients and methods. Since March 2008. until May 2012. eighty-five patients (27 male and 58 female) aged between 10 and 22 years treated with upper or/and lower fixed orthodontic appliance were included in the study. Orthopantomography was done for all patients before the beginning of orthodontic therapy and after the removal of fixed appliances and for 35 patients computerized tomography of two or three adjacent teeth was done in the same time. The tooth root length in both jaws was determined by using ortopantomography only for teeth with completed root formation. Measurements were performed for central and lateral incisors, canines, first and second premolars and first molars. The tooth root length on orthopantomograms and computerized tomograms was determined as the distance between the enamel-cementum margin and apex of tooth root. The root length for all examined teeth was measured mesially and distally directly on ortopantomograms using calibrated ruler to the nearest 0.5 mm and using i-Dixel and Syngo Fastview softver for analizes of computerized tomograms. The alveolar bone height was determined both on orthopantomograms and computerized tomograms for all examined teeth as the distance between root apex and the most coronary placed alveolar bone point with normal periodontal space width of 0.5 mm. The value of root and alveolar bone loss is determined by comparing the values of root lenght and alveolar bone height measured on orthopantomograms and computerized tomograms before and after orthodontic therapy. Finally, the changes in periodontal ligament and cortical alveolar bone width during orthodontic therapy were also determined using computerized tomography. Results. During the active phase of orthodontic treatment the most pronaunced root resorption among upper teeth was determined on second right premolars (0.6605 mm/4.3908 % mesially and 0.8661 mm/5.6738 % distally) and second (0.7274 mm/4.2264 % mesially) and first (0.6929 mm/4.3175 % distally) left premolars..