Adsorption of neodymium,terbium and dysprosium using a synthetic polymer-based magnetic adsorbent

In this study,a polyamide with methine-thiophene and pyrimidine linkages(poly(pyrimidine-thiophene-amide)(PPTA)) was synthesized.Then,magnetic PPTA(M-PPTA) was synthesized using the hydrothermal technique.The products were analyzed by Fourier-transform infrared spectroscopy(FTIR),nuclear magnetic resonance(NMR),X-ray diffraction(XRD),thermogravimetric analysis(TGA),field-emission scanning electron microscopy(FE-SEM),and a vibrating-sample magnetometer(VSM).The nanocomposite exhibits a saturation...     

Free-energy profile of the reaction catalyzed by triosephosphate isomerase

The experimental results on the interconversion of dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate catalyzed by triosephosphate isomerase that are presented in the previous five papers are here collected and analyzed according to the theory presented in the first paper (Albery, W.J., Knowles, J.R. (1976), Biochemistry 15, the first of eight papers in a series in this issue). The rate constants and fractionation factors so derived allow the construction of theGibbs free-energy profile for this enzyme-catalyzed reaction.     

Free-energy simulations of the retinal cis --> trans isomerization in bacteriorhodopsin

Free-energy profiles for ground-state cis --> trans isomerization of retinal in vacuum, in solution, and in the protein bacteriorhodopsin are calculated using free-energy simulations. The free-energy barriers in the protein were 9 kcal/mol for ionized Asp85 and 14 kcal/mol for neutral Asp85, significantly lower than those found in solution (18 kcal/mol) or vacuum (19 kcal/mol). Therefore, bacteriorhodopsin can be said to act as a catalyst in the isomerization. The barrier in the protein is due mainly to stabilization of the transition state through favorable nonbonded interactions with the protein part of the system, with internal strain and interactions with solvent playing minor roles. The protonated Asp85 simulation models the behavior of the system in the N --> O transition. Our calculated 14 kcal/mol barrier and 4-ms relaxation time for this process are in excellent agreement with experimentally measured values of 12 kcal/mol and 5 ms, respectively. The ionized Asp85 simulation models two hypothetical processes: the N --> O transition with a proton removed from Asp85 and the initial BR568 --> L transition on the ground-state energy surface. The cis-trans isomerization barrier in this system is 9 kcal/mol, the lowest of all the studied cases. The presence of the charged carboxylate group in the ionized Asp85 system leads to strong stabilization of the transition state by interactions with the surroundings and changes the distance between Asp85 and the Schiff base proton compared to the corresponding distance in the neutral Asp85 system. This suggests that the protonation of Asp85 plays an important role in regulating access to the Schiff base proton. For both Asp85 ionization states the calculated cis-trans free-energy difference was close to 0, indicating that the protein can accommodate both retinal isomers equally well. The computed negligible difference between the N and O free-energy levels is in accord with experimental data.     

Synthesis of neodymium aluminide by aluminothermic reduction of neodymium oxide

Neodymium aluminide was synthesized from Nd₂O₃ under vacuum by aluminothermic reduction in an induction furnace. Although the standard free energy change associated with the reduction of Nd₂O₃ by Al is positive, due to the formation reaction of the intermetallic compound, it was possible to drive the reaction in the forward direction in the presence of excess Al. An attempt was also made to reduce Nd₂O₃ by Al in the thermit process in the presence of the Fe₂O₃-Al thermit mixture so as to make the reaction self-sustaining. A comparison between these two processes was made with respect to the reduction of Nd₂O₃ by Al. Differential thermal analysis (DTA) was used to study the reaction process. The product was characterized by x-ray diffraction (XRD), x-ray fluoroscence (XRF), electron probe microanalysis (EPMA), and optical metallography (OM).     

Comparison of rare earths doping(neodymium and samarium) on structural and magnetic properties of Ni-Zn-Bi nanoferrites

Excellent magnetic properties in ferrites are required for high-frequency applications and for wastewater treatment. Thus, the present study shows the comparison of magnetic and structural properties of Nd and Sm substituted Ni—Zn—Bi ferrites with the series Ni_0.5Zn_0.5Bi_0.04Nd_xFe_1.96-xO₄(with step size 0.002)and Ni_0.5Zn_0.5Bi_0.04Sm_xFe_1.96-xO₄(with step size 0.02) pre...     

Presence of neodymium and gadolinium in cobalt ferrite lattice:Structural,magnetic and microwave features for electromagnetic wave absorbing

In this work,neodymium substituted gadolinium-cobalt ferrite nanoparticles were synthesized by hydrothermal method.The significant role of doping both the Nd~(3+)and Gd~(3+) ions to cobalt ferrite in manipulating the cation distribution and further in influencing structural and magnetic properties was experimentally studied and reported.The influence of Nd~(3+) substitution was investigated with step of 0.02-0.1 into the optimized Gd-Co compound.The crystal structure formation and crystallite size were explored by X-ray diffraction analysis in which the crystallite size and lattice constant decrease with increasing the Nd~(3+) substitution.The microstructural properties were studied by field emission scanning electron microscopy and atomic force microscopy studies.The obtained structural and morphological results reveal that the substitution of Nd~(3+) with more than 0.06 into the Gd-Co ferrites will change the material be havior and trends.The saturation magnetization and coercivity values were measured using a vibration sample magnetometer at room temperature.Comparative microwave absorption experiments demonstrate that the reflection loss properties enhance with increasing substitution of Nd~(3+) cations in Gd-Co ferrite spinel structure.This research reports that the as-prepared Nd~(3+) substituted Gd-Co ferrite compound stands as promising candidate for absorbing electromagnetic wave with a wider absorbing bandwidth of X-band.