The objective was to evaluate and assess the surface quality of fixed orthodontic appliances after intraoral usage for several months. Nine sets of orthodontic brackets by three different manufacturers and twelve archwires differing in chemical composition were analyzed in a scanning electron microscope with an energy dispersive X-ray analyzer for signs of corrosion. Obtained results showed that the majority of the evaluated appliances displayed no traces of corrosion. Machining or casting defects hardly ever act as the origins of corrosion processes. However, some samples displayed signs of corrosion of a galvanic and pitting nature. The authors claim, that despite the surface defects, most of the appliances were able to retain the desired corrosion resistance, although in some cases these flaws could act as the origin of corrosion processes.
Raz Muhammad, Muhammad Uzair, M. Javid Iqbal, M. Jawad Khan, Yaseen Iqbal and Carlos R. Rambo
(A n B n O3 n+2 , n = 4) was claimed to be the first ferroelectric [ 7 ]. Similarly, other oxides of A n B n O3 n+2 (n = 4) which are non-centrosymmetric, such as A 2 Nb 2 O 7 (A = Ca, Sr) and Ln 2 Ti 2 O 7 (Ln = La, Nd), comprise the ferroelectrics with the highest Curie temperature (T c ) [ 8 ]. In general, the oxides with n = 2, 3 (II), 4 and 6 are non-centrosymmetric and exhibit ferroelectricity while the uneven types, n = 3 (I), n = 5 or n = 7 are centrosymmetric [ 8 , 9 ]. Ca 2 Nd 4 Ti 6 O 20 (CNT) is a non-centrosymmetric compound which belongs to A n B
as photosensitive compounds.
Nishikubo et al.  claimed that the novel p-alkylcalix[n]arene showed photochemical reactions. Several cinnamate based photocrosslinkable polymers were synthesized by Perny et al.  . Subramanian et al.  reported the synthesis of several photocrosslinkable polymers containing the p-methoxy (or chloro) substituted chalcone moiety. They also claimed that these polymers cannot be sensitized but have high photosensitivity. The liquid crystalline alignment of poly(vinyl cinnamate) and poly(7-methacryloyloxycoumarine) in the
H. Koralay, O. Hicyilmaz, S. Cavdar, O. Ozturk and A.T. Tasci
phase values were obtained in the range of 741.0 to 786.1 K and 796.8 to 819.8 K, respectively. Exothermic peaks, formed around these temperatures, were claimed to occur due to nucleation [ 29 , 30 ] in the BSCCO system.
DTA curves of Bi 1.8 Sr 2 Ca 2 Cu 2.5 Zn 0.5 O 10+δ sample for various heating rates (a) β = 5 K.min-1, (b) β =10 K.min-1, (c) β = 15 K.min-1 and (d) β = 20 K.min-1.
DTA results of Bi 1.8 Sr 2 Ca 2 Cu 3.2-x Zn x O 10+δ (x = 0, 0.1, and 0.5) samples.
Heating Rate (β) [K_min -1 ]
Raminder Preet Pal Singh, I.S. Hudiara and Shashi Bhushan Rana
is due to intrinsic coupling between the atoms of doped materials but not due to the presence of metallic clusters or secondary phases.
However, there are certain studies which claim that ferromagnetic behavior in transition metal-doped ZnO is correlated with defects such as oxygen or zinc vacancies [ 30 – 32 ]. Further, in some studies, the correlation between intrinsic defects such as oxygen or Zn vacancies and magnetism is also discussed [ 33 , 34 ]. Karmakar et al. [ 35 ] investigated the origin of ferromagnetism in Fe-doped ZnO using ESR and M
Reham M. Abdel Fattah, Hala A. Kiwan, Awad I. Ahmed and Mohamed R. Mostafa
Metal oxides have a wide range of industrial applications including chemical sensors, microelectronic materials, ceramics and catalysis. In heterogeneous catalysis, metal oxides can be used as either active catalysts or supports for dispersing catalytically active metal catalysts [ 1 , 2 ].
Among various metal oxides, zirconia is of a particular interest and has received widespread attention due to its thermal stability and mechanical properties. Moreover, zirconia is claimed to be a good catalyst that has acidic, basic, reducing and
crystal lattice of the samples [ 22 , 23 ]. The strain observed in the samples can be explained by the Uniform Deformation Model (UDM) using Williamson-Hall (W-H) plot [ 22 , 24 ] which claims that the diffraction line broadening is due to strain (є) effect and reduction in crystallite size. The UDM equation was calculated by using the diffraction peak broadening and is given by [ 22 , 24 ]:
β cos θ = k λ / d + 4 ε sin θ $$\beta \cos \theta = k\lambda /d + 4\varepsilon \sin \theta$$
This equation represents the Uniform Deformation Model (UDM) which
E. Talik, L. Lipińska, A. Guzik, P. Zajdel, M. Michalska, M. Szubka, M. Kądziołka-Gaweł and R.L. Paul
samples with x = 0.4 and 0.5 are in ordered state. They have the highest admixture of Fe3d states in the valence band. However, the features A to D are difficult to distinguish. Both above mentioned reasons can be responsible for the change of the shape of the valence band states.
For Ni containing samples, the shapes of the valence bands are similar, blurred (not visible Mn3de g states (feature A). This may reflect not only the paramagnetic state but the admixture of the second phase, as well.
There are some theoretical papers claiming that existence of Mn 3+ LS