Synthesis and characterization of Ag-doped cerium oxide nanoparticles for electromagnetic radiation shielding.

In the current study, CeO2: Ag (0 and 11 mol) nanoparticles (NPs) were synthesized by solution combustion method using Aloevera extract as reducing agent. As-obtained NPs were characterized by standard techniques. Bragg's reflections confirm the formation of a single-phase cubic structure of CeO2:Ag NPs. Crystalline size is calculated using both the W-H plot and Scherrer's equation. Crystallite size found to decrease with increase in the dopant concentration. EDAX pattern confirmed the presence of Ce, O and Ag. Direct energy band calculated using Wood and Tauc's was found to be in the range of 2.9-2.2 eV for 0 and 11 mol, respectively. Fourier transformation infrared spectroscopy (FTIR) analysis confirmed the presence of the functional groups. Total shielding efficiency (SET) will give the best representation of EMI shielding properties. SET values calculated for a wide range of wavelengths are found to be as follows: near infrared (1.65 × 102 dB), mid infrared (9.78 × 101 dB) and far infrared (6.32 × 101 dB), followed by microwave region (MW) (6.46 × 101 dB), ultra-high frequency (UHF) (7.31 × 101 dB), very high frequency (VHF) (8.27 × 101 dB), high frequency (HF) (9.26 × 101 dB), medium frequency (MF) (1.02 × 102 dB), low frequency (LW) (1.12 × 102 dB), very low frequency (VLF) (1.22 × 102 dB), ultra-low frequency (ULF) (1.42 × 102 dB) and extremely low frequency (ELF) (1.52 × 102 dB). SET values of CeO2:Ag NPs are compared with other traditional materials and nanocomposites and found to be potential use in EMI shielding applications.

Synthesis and characterisation of Zn-doped cerium oxide nanoparticles for electromagnetic radiation shielding.

CeO2-NPs (nanoparticles) exhibit a variety of properties, which have prompted researchers to explore various applications, such as gas sensing, biomedical, Electromagnetic Interference (EMI) shielding, etc. Zn-doped CeO2-NPs with concentrations ranging from 7 to 11 mol were synthesised using Aloe vera extract as a reducing agent by the solution combustion method. As obtained, NPs were characterised by standard techniques. Braggs reflections confirm the formation of a single-phase cubic structure of CeO2Zn NPs. Crystalline size is calculated using both the W-H plot and the Scherrer equation, which were found to be 12 and 9 nm, respectively. The Energy-dispersive X-ray analysis (EDAX) pattern confirmed the presence of Ce, O and Zn. The direct energy band values are found to be decreasing from 3 to 2.87 eV with an increase in the doping concentration of Zn from 7 to 11 mol. Total shielding efficiency (SET) will give the best representation of shielding properties. The SEt values of CeO2Zn NPs are compared to those of other conventional materials and NP materials, finding significant applications in EMI shielding.

Review of postcontrast MRI studies on diffusion of human lumbar discs.

Diffusion is the only source of nutrition to the intervertebral discs, and alteration of diffusion is considered to be the final common pathway for disc degeneration. Yet diffusion remains poorly understood due to the paucity of reliable methods to study diffusion noninvasively in humans in vivo. In recent years, postcontrast MRI has emerged as a powerful and reliable tool for analyzing diffusion in lumbar discs. Since it is noninvasive and safe, it can be used to document the process of diffusion temporally over a period of 24 hours. Well-designed studies have shown that diffusion is a very slow process, and that the endplate is the main structure that controls the process of diffusion. Contrast MRI studies have also made it possible to identify endplate breaks in vivo. In the future this technique may be applied to study the influence of smoking, mechanical loading of the discs, abnormal posture, and atherosclerosis of the lumbar arteries on diffusion. These conditions have all been implicated in disc degeneration through a final common pathway of altered diffusion and decreased nutrition. This review article focuses on the current knowledge, methodology, various factors that influence the diffusion properties of the discs, and future applications of this promising technique.

ISSLS prize winner: A study of diffusion in human lumbar discs: a serial magnetic resonance imaging study documenting the influence of the endplate on diffusion in normal and degenerate discs.

STUDY DESIGN: An in vivo serial magnetic resonance imaging study of diffusion characteristics in human lumbar discs over 24 hours in healthy volunteers and patients with low back pain. OBJECTIVES: To document the temporal pattern of diffusion in normal human lumbar discs and to study the influence of the vascularity of bone and the status of endplate on diffusion in the normal and degenerate discs. SUMMARY OF BACKGROUND DATA: Diffusion is the only source of nutrition to the discs, but no firm data are available on pattern of diffusion in humans. More data on this important subject are required to improve our understanding of disc degeneration and to probe research possibilities for preventing the same. METHODS: The diffusion pattern over 24 hours following gadodiamide injection was studied in 150 discs (96 normal and 54 degenerate). Signal intensity values for three regions of interest in bone (i.e., vertebral body, subchondral bone, and endplate zone) and seven in the disc were calculated, and normal percentiles of diffusion were derived for these regions. Enhancement percentage for each time period, peak enhancement percentage for each region, and the time taken to achieve peak enhancement percentage (Tmax) were used to define and compare diffusion characteristics and plot a time-intensity curve to document the 24-hour temporal pattern. The correlation of blood flow of the bone as measured by peak enhancement percentage of vertebral body, the status of the endplate zone as measured by the peak enhancement percentage, and Tmax of the endplate zone were correlated with the diffusion of the disc.Univariate analysis of variance, multiple comparisons, appropriate tests for significance, and stepwise linear regression analysis were used for analysis of the data using SPSS software. RESULTS: In normal discs, a "diffusion march" from the vertebral body to the center of disc was noted with the SImax being observed at 5 min in the vertebral body and subchondral bone, at 2 hours in the endplate zone, and at 6 hours in the nucleus pulposus. A significant difference in mean peak enhancement percentage was observed between that of the body and the discs in those less than 10 years and those above the age of 20 years (P < 0.001). Alterations in endplate zone produced distinct magnetic resonance imaging signs of disturbance in diffusion, which offered a reliable noninvasive method of identifying endplate cartilage damage. Stepwise linear regression analysis showed that the significant variable influencing diffusion to the center of the nucleus pulposus of the total sample was peak enhancement percentage of endplate zone (R2 = 0.216; P < 0.001), that of degenerate discs was peak enhancement percentage of endplate zone (R2 = 0.322; P < 0.001), and that of normal discs (R2 = 0.324; P < 0.001) was age. CONCLUSIONS: Serial postcontrast magnetic resonance imaging studies offer a reliable method of assessing the diffusion of the discs and the functional status of the endplate cartilage. Endplate cartilage damage increases with age and produces considerable changes in diffusion. The present study has described reliable signs by which these damages can be identified in vivo. Aging and degeneration have been shown to be two separate processes by documenting clear-cut differences in diffusion. The present data encourage use of diffusion studies as a noninvasive method to assess the physiologic status of the disc and endplate and to study the effect of drugs, smoking, mechanical loading, exercises, etc. on the physiology of the disc.