Central Resonance Line Research Articles

Investigation of radiosterilization feasibility of sulfamethoxazole by ESR spectroscopy

ABSTRACTIn the present study, the spectroscopic features of the radiolytic intermediates that were produced in gamma-irradiated (5, 10, 25 and 50 kGy) sulfamethoxazole (SMX) have been investigated by electron spin resonance (ESR) spectroscopy and the radiation sterilization feasibility of SMX by ionizing radiation was examined. Gamma-irradiated SMX exhibited a complex ESR spectrum consisting of 13 resonance lines where spectral parameters for the central resonance line were found to be g = 2.0062 and ΔHpp = 0.6 mT. The radiation yield of SMX was calculated to be relatively low (G = 0.1) by ESR spectroscopy and no meaningful difference was observed in the comparison of unirradiated and 50 kGy gamma irradiated SMX by the Fourier transform infrared (FT-IR) technique, confirming that SMX is a radioresistive material. Although SMX could not be accepted to be a good dosimetric material, the identification of irradiated SMX from the unirradiated sample was possible even for the low absorbed radiation doses and for a relatively long time (three months) after the irradiation process. Decay activation energy of the radical species, which is mostly responsible for the central intense resonance line, is calculated to be 45.15 kJ/mol by using the signal intensity decay data derived from annealing studies. Four radical species with different spectroscopic properties were accepted to be responsible for the ESR spectra of gamma-irradiated SMX, by simulation calculations. It is concluded that SMX and SMX-containing drugs can be sterilized by gamma radiation and ESR spectroscopy is an appropriate technique for the characterization of these induced radical intermediates during the gamma irradiation process of SMX. Toxicology tests should also be done for its safe usage.

Feasibility of radiation sterilization and dosimetric features of ampicillin: an electron spin resonance study

ABSTRACTIn the present work, it was aimed to identify radical species produced by gamma irradiation (3–34 kGy) of solid ampicillin, to determine its spectroscopic, dosimetric, stability and kinetic behavior, and to investigate feasibility of the radiation sterilization feature of ampicillin by using electron spin resonance (ESR) spectroscopy. ESR experiments were performed at low and high temperatures (130–400 K) to examine the characteristic properties of the radical intermediates that are produced in ampicillin by gamma radiation treatment. Unirradiated ampicillin presented no ESR signal but irradiated samples exhibited ESR spectra with four resonance peaks spread over a magnetic field range of 8 mT. The spectral parameters of the central resonance line of the spectrum are g = 2.0044 and ΔHpp = 0.08 mT. An exponential growth function of the applied dose was found to describe best the experimental dose–response data and it was found that ampicillin did not exhibit the feature of a good dosimetric material as its ESR intensity was relatively weak even for the samples irradiated at high level of doses. Gmean value of gamma-irradiated ampicillin was found to be 4.6 ± 0.9 × 10−9 mol/J, which is very small compared to irradiated alanine solid sample. However, the discrimination of irradiated ampicillin from unirradiated one was possible even ∼3 months after storage at normal conditions. The simulation calculations indicated that gamma irradiation created two different radical species in solid ampicillin. Decay activation energy of the radical species which is mostly responsible from central intense resonance line is calculated to be 55.6 ± 3.2 kJ/mol by using the signal intensity decay data derived from annealing studies. It was concluded that ampicillin could be sterilized by gamma radiation and ESR spectroscopy can be used as a potential technique to monitor its radiosterilization process.

Study on the paramagnetic relaxation mechanisms by R87b nuclear magnetic resonance in Rb2MnCl4 crystals of A2BX4 type

The spin-lattice relaxation time, T1, for R87b nuclei in Rb2MnCl4 crystals was investigated, and a phase transition was found near 383 K (=TC). The R87b spectrum changes near TC from two central resonance lines due to Rb(1) and Rb(2) to one Rb central resonance line, and this change is due to changes in the local symmetry of the Rb sites near TC. The central resonance lines for Rb nuclei in Rb2MnCl4 crystals are shifted to higher frequencies by the paramagnetic ions. Further, the relaxation times for the Rb(1) and Rb(2) nuclei in Rb2MnCl4 crystals are more or less continuous near TC. Below TC, the spin-lattice relaxation rates, T1−1, for Rb(1) and Rb(2) are proportional to T−2, which implies that these relaxations occur mainly via Raman processes. We also compare our results for Rb2MnCl4 with those reported previously for Rb2BCl4 (B=Co and Zn) and CsBCl3 (B=Mn, Cu, Zn, and Cd) crystals.

Relaxation mechanisms of Rb 2Co(SO 4) 2 ⋅ 6H 2O single crystals studied by 1H and 87Rb nuclear magnetic resonance

The spin-lattice relaxation time, T 1 , and the spin–spin relaxation time, T 2 , for 1 H and 87 Rb nuclei in Rb 2Co(SO 4) 2⋅6H 2O crystals were investigated. The phase transitions occur near 370 K ( = T C 1 ) , 402 K ( = T C 2 ) , 413 K ( = T C 3 ) , and 458 K ( = T C 4 ) . The 87 Rb spectrum changes near T C 1 from Rb(1) and Rb(2) central resonance lines to one Rb central resonance line, and this change is due to the structural phase transition. The change in the 1 H T 1 near T C 1 and the changes in T 1 and T 2 for Rb(1) and Rb(2) near T C 1 and T C 2 are also due to the phase transitions, and are related to changes in the symmetry of the octahedra of water molecules and slight rotations of the SO 4 tetrahedra surrounding Rb +. Further, below T C 1 the spin-lattice relaxation rates, T 1 − 1 , for Rb(1) and Rb(2) are proportional to T − 2 , which implies that these relaxations occur mainly via Raman processes.

Spin-lattice relaxations of Be9 and Al27 in single crystalline alexandrite

Nuclear spin-lattice relaxations of Be9 and Al27 in an alexandrite (BeAl2−xCrxO4, x=0.02) single crystal have been investigated in the temperature range 140 K–400 K. The paramagnetic impurity effect on the relaxation is negligible for both nuclei. The relaxation of the Be9 nuclear spins is found single exponential in time when the whole resonance lines are uniformly excited. When only the central resonance line is excited for Al27, the relaxation is well fitted with a linear combination of three exponential functions given by Simmons et al. [Phys. Rev. 127, 1168 (1962)]. Since the spin-lattice relaxation rate is proportional to the square of temperature for both nuclei, the dominant relaxation mechanism in this temperature range can be inferred as the Raman process.

Interaction of Paclitaxel with Phospholipid Bilayers

AbstractPaclitaxel is an effective anticancer drug. Recently, paclitaxel encapsulated in liposomes was promoted as a better tolerated pharmaceutical formulation than that currently in use. The data presented in this study show the effects of paclitaxel on phospholipid bilayers. Experiments involving the phospholipid head group probe CAT-16 show significant disordering of the interfacial region. The pretransition was abolished and the main phase transition temperature in paclitaxel loaded liposomes was reduced. 2T II values of 7-NSA and 16-NSA spin probes reporting from the middle and from the core of the phospholipid bilayer, respectively, show that the presence of paclitaxel eliminated the pretransition (from Lβ/ to Pβ/) while inducing a slight reduction in the main (Pβ/ to Lα) phase transition temperature; in the same temperature interval, the central resonance line width δ H O displayed a greater rate of spin label reorientation in paclitaxel loaded bilayers. Further data are presented clearly demonstr...

Nuclear magnetic resonance of 197Au in gold metal

By the use of the single-OPW, the expressions for the spin-lattice relaxation time T 1 (Q) due to the quadrupole interaction and the second moment for the central resonance line are calculated, taking account of the electron interaction. The numerical calculation leads to T 1 (Q)T = 32 secK which is considerably large in comparison with the value, 13 secK, estimated from the deviation from the Korringa relation. When the single-pseudo-wave function is used, a reasonable value is obtained. The second moment of the central line of 197 Au is calculated by taking account of the effect of strained crystals for the quadrupole moment. It is found that main contributions to the line-width come from the exchange and pseudo-dipole interactions. Some examinations are made for the discrepancy of Stoner's enhancement factor in noble metals between our analysis and the band calculation.

Quadrupole and anisotropic knight-shift effects in V 3Au in the normal state

The NMR spectra of V 3Au samples with different degrees of atomic ordering have been investigated. The central resonance line and the first quadrupole satellites could be detected. The position and width of these lines as a function of the applied magnetic field strength were determined. The shape of the central line gives information about the anisotropy of the Knight shift, whereas the position of the satellites gives information about the electric field gradients (EFG) in this compound. It is shown that the definition of the Knight shift from the satellites is more meaningful than the Knight shift derived from the central line. Anisotropic effects have been studied more thoroughly than in the previous research. EFG values of the differently ordered samples are compared with each other. Precision lattice-parameter measurements were made and they show that the V—V separation in all of our samples varies by less than 0.05%. There appears to be no evidence of a correlation between the EFG and the density of states of the electrons at the Fermi level: N( E F).

Acoustic saturation of nuclear magnetic resonance lines

Study has been made of the effect of acoustic power applied at twice the Larmor frequency on the individual nuclear magnetic resonance lines in the presence of radio-frequency power. When\(W''_{u2} (W_{u\tfrac{1}{2} \to - \tfrac{3}{2}} )\) is finite and other ultrasonic transition probabilities are zero, one obtains the same acoustic saturation behaviour for the central resonance line for the quadrupolar and the magnetic relaxations. For an arbitrary spinI, this expression has been generalized. However, the central resonance line remains unaffected when ultrasonic transition probabilities other than\(W''_{u2} \) are finite separately. The effect of the acoustic power on the satellites for different cases is studied in great detail. Some of the satellites are affected and a few are unaffected. Some of the affected satellites show interesting behaviour in the sense that, instead of the regular saturation behaviour, enhancement effect and negative ratios of the population difference to its equilibrium value are obtained for higher values ofU which is a measure of acoustic power.

Acoustic saturation of nuclear magnetic resonance lines

Study has been made of the effect of acoustic power applied at twice the Larmor frequency on the individual nuclear magnetic resonance lines in the presence of radio-frequency power. When\(W''_{u2} (W_{u\tfrac{1}{2} \to - \tfrac{3}{2}} )\) is finite and other ultrasonic transition probabilities are zero, one obtains the same acoustic saturation behaviour for the central resonance line for the quadrupolar and the magnetic relaxations. For an arbitrary spinI, this expression has been generalized. However, the central resonance line remains unaffected when ultrasonic transition probabilities other than\(W''_{u2} \) are finite separately. The effect of the acoustic power on the satellites for different cases is studied in great detail. Some of the satellites are affected and a few are unaffected. Some of the affected satellites show interesting behaviour in the sense that, instead of the regular saturation behaviour, enhancement effect and negative ratios of the population difference to its equilibrium value are obtained for higher values ofU which is a measure of acoustic power.

Transmission and line broadening in the Mössbauer effect. II

Calculations expressing the shape of the Mössbauer line to be expected in a transmission-type experiment are extended to the case where both emission and absorption spectra are split by a hyperfine interaction. To see the effects of spectral shape, Gaussian as well as Lorentzian spectra are considered. The results indicate that the characteristics of the transmitted line are strongly dependent upon the spectral shape. To test the calculations, the transmitted line shape was measured as a function of absorber thickness. These experiments were performed with the 14.4 keV radiation emitted by Fe 57. To obtain unsplit spectra, Type 310 stainless steel was used for both source backing and absorbers. The observed line was more than four times as wide as the natural width, and was neither Lorentzian nor Gaussian. An unambiguous comparison with the calculations is therefore impossible. Averaging the results of analyses based on Lorentzian and Gaussian shapes yields f=67%, f′ A=137% for those source and absorber recoilless fractions. Identically split spectra were obtained by using Armco iron for the source backing and the absorbers. In this case, the central resonance line was approximately Lorentzian. Applying the corresponding analysis yields f=67%, f′ A=144%. These anomalously high values of f′ A were obtained by using a conversion coefficient of15. To obtain reasonable values, a conversion coefficient of about 8 is required.