[en] The study was aimed to perform a radiation dose audit by measuring entrance skin dose (ESD) to patients during digital radiography (DR) examinations in different X-ray centers of Uttarakhand, India. It was also intended to compare the dose results of the patient dose survey with established diagnostic reference levels (DRLs)

[en] Diagnostic X-ray imaging is the largest contributor to total population radiation exposure from man-made radiation sources. This is attributed to better technology and growing usage of diagnostic X-ray imaging methods. Patient dose involved in a diagnostic X-ray examination is a function of several parameters such as performance of X-ray machine, type of image receptor and selection of exposure parameters. The International Commission on Radiological Protection (ICRP) recommends that the patient doses should be measured on regular basis to optimize patient protection. So under realistic conditions of exposure, patient dose should to be estimated and verified against the established national diagnostic reference level (NDRL). DRLs for radiographic projections are often expressed in terms of the entrance skin dose (ESD), which is a measure of the amount of energy imparted per gram of tissue at the entrance surface

[en] Co_0.8Fe_2.2O₄ nano ferrite has been synthesized by sol gel auto-combustion method. X-ray diffraction (XRD) and Mossbauer spectroscopy were used to characterize the synthesized as burnt and thermally annealed (600 ^oC for 3 hours) samples. Both XRD and Mossbauer measurements confirm the formation of spinel phase with Scherrer's grain diameter ( D _s) ≈ 37 nm. Presence of α-Fe and, Fe₂O₃ was also observed. Thermal annealing induced decrease of ρ _xrd (from 5267.9 to 5262.7 Kg/m³) for the annealed samples is ascribable to the fact that, increase of unit cell volume overtakes the increase in mass of the unit cell. Comparison of dry gel and thermally annealed sample shows that in dry gel, B site is more populated with Fe ions, whereas thermal annealing leads to migration of Co from A to B site with simultaneous migration of Fe from B to A site, thus dropping the Neel magnetic moment. Bond angle values clearly reveal that thermal annealing leads to strengthening of B-O-B interaction with simultaneous wreaking of A-O-B, and, A-O-A interaction. (paper)

[en] Entrance skin dose (ESD) was calculated based on the X-ray beam output, the exposure parameters used for the actual examination and the standard value of backscatter factor. Descriptive statistics were generated from the data by using Microsoft Excel 2010. The third quartile values of ESDs obtained in this study for different X-ray projections of chest anterior-posterior (AP), chest posterior-anterior (PA), cervical spine, thoracic spine, lumber spine AP, lumber spine lateral, abdomen, KUB, pelvis, skull and knee joint were 0.79, 0.28, 1.20, 2.80, 4.26, 9.82, 2.68, 3.21, 2.69, 2.21 and 0.55 mGy respectively. The ratio of maximum to minimum ESD values ranges from 5.2 for thoracic spine to 19.76 for chest AP X-ray examinations. In general, the obtained ESD values were found to be either lower than or in agreement with the reported national/international values

[en] Zn addition induced modification of cationic distribution for tuning magnetic properties of Li_0_._5_-_x_/_2Zn_xFe_2_._5_-_x_/_2O_4 (x = 0, 0.1, 0.25, 0.3, 0.5, 0.7, 0.9, 1.0) powders is studied by x-ray diffraction (XRD) and magnetic measurements. XRD shows the formation of cubic spinel structure, with Scherrer’s grain diameter ranging between 26.7 to 37.8 nm. With Zn addition, oxygen anions are displaced in such a way that the A-B interaction weakens, whereas A-A and B-B interaction strengthens; furthermore it also pushes Fe"3"+ and Li"1"+ ions to B site, leading to changes in magnetic properties. Highest saturation magnetization (M_s) of 64.6 A m"2 / kg was obtained for sample with x = 0.25 and lowest coercivity (H_c) of 4949.9 A/m was obtained for the sample with x = 0.7. Calculated values of experimental magnetic moment ‘n_B’ and Neel magnetic moment ‘n_N’, display similar trend as that of M_s. Present results very clearly show a strong correlation between Zn-addition induced changes in cation distribution and magnetic properties, which can be utilized effectively for tuning magnetic properties.

[en] Mg_1−xZn_xFe₂O₄ (with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) spinel ferrite was synthesized via sol-gel auto combustion method. XRD confirms the formation of spinel phase with a secondary phase of Fe₂O₃ (in case of x = 1.0). Structural parameters changes as the Zn concentration increases which can be ascribed to the replacement of an ion with lower ionic radius (Mg²⁺) with that of an ion with higher ionic radius (Zn²⁺). Variation in the magnetic properties with Zn content are interpreted in terms of migration of Fe³⁺ between tetrahedral and octahedral sites.

[en] Soft magnetic Mg_0.1Ni_0.3Zn_0.6Fe₂O₄ and hard magnetic BaFe₁₂O₁₉ bulk nanocrystalline ferrites were synthesized using the sol-gel auto-combustion method, and were used as targets to deposit soft-hard thin films by the pulsed laser deposition (PLD) method. Various soft-hard thin films with different preparation conditions were deposited on Si (100) substrate, which can be effectively utilized to get better magnetic properties. The prepared films were characterized by the X-ray diffraction (XRD), atomic force microscopy (AFM) and magnetic measurements. XRD confirms the presence of soft and hard phases in the thin films. Coercivity of the prepared films ranges from 1.67 to 2.66 kA/m. AFM images show clustering of grains at the film surface with a characteristic columnar growth.

[en] Highlights: • Non-equilibrium cation distribution is induced by sol-gel auto-combustion synthesis. • Structural and magnetic properties are strongly influenced by cation distribution. • The increase of Zn-concentration induces a significant decrease in coercivity. • Static and dynamic energy losses increase as a function of vertex field. Co_1-xZn_xFe₂O₄ (0.08 ≤ x ≤ 0.56) powders prepared by a sol-gel auto-combustion method have been investigated through the combined use of structural and dc/ac-magnetization measurements under a wide range of applied magnetic field values. EDS spectra are performed to evaluate the samples chemical composition, whereas the X-ray diffraction measurements indicate the formation of the typical nanocrystalline mixed cubic spinel structure and allow to determine the cationic distribution as well as the lattice parameter and the oxygen position as function of Zn content. Magnetic characterization improves the knowledge about the correlation between the structural properties and magnetic behavior. The magnetization curves show a hysteretic behavior at room temperature and they are analyzed as function of Zn content taking in account the Yafet-Kittel’s model. The replacement of non-zero magnetic moment Co²⁺ ions with zero magnetic moment Zn²⁺ ions induces a gradual reduction of magnetocrystalline anisotropy and a lowering of the magnetic coercivity. The energy lost in a static and alternating magnetic field (frequency of 69 kHz) at selected vertex field values for the studied samples has been calculated in order to evaluate their prospective usage to operate in different field conditions.

[en] Effect of swift heavy ion irradiation on MgFe₂O₄ (annealed at 450 °C/3 h) sample prepared by a sol–gel auto-combustion procedure has been studied. Single phase samples were irradiated with 120 MeV ²⁸Si⁹⁺ with ion fluence: 1 × 10¹¹, 1 × 10¹², and 1 × 10¹³ ions/cm² to monitor its effect on the structure, cation distribution, and magnetic properties. Electronic energy loss induced modifications of cation distribution, structural, magnetic properties were examined by XRD, VSM, FE-SEM, and EDS. XRD measurements show the formation of single phase nanocrystalline mixed cubic spinel structure (grain size 31–35 nm). Observed slight changes of experimental lattice parameter with increasing irradiation dose is ascribable to the migration of Mg²⁺ ions (ionic radius: 0.071 nm) from B to A site with simultaneous migration of Fe³⁺ ions (ionic radius: 0.063 nm) from A to B site. Sample irradiated at a lower fluence (1 × 10¹¹ ions/cm²) has higher specific surface area (S), is more suitable for catalytic activity. Irradiation leads formation of dead layer, thus affects magnetic properties, via spin canting at surface. Therefore, irradiation can be used to control both structural, magnetic properties. SEM images display agglomerated nano-particles, while EDS pattern confirms the presence of Mg, Fe and O elements in the sample. First time the antistructural modeling for magnesium ferrite is reported to get information on active surface centers.