D. Mehta

Measurements of L X-ray fluorescence cross sections and yields for elements in the atomic range 41 ≤ Z ≤ 52 at 5.96 keV

Abstract Total L X-ray fluorescence (XRF) cross sections have been measured for ten elements in the atomic range 41 ≤ Z ≤ 52 at 5.96 keV. It is observed that the measured L XRF cross-section values for the elements in this region are in general agreement with the theoretical ones evaluated using L Subshell fluorescent yields (ωi) and Coster-Kronig transition probabilities (ƒ ij ) based on the Relativistic Dirac-Hartree-Slater theory. The average L shell fluorescence yields ( ω L ) have also been computed using the presently measured cross-section values and the theoretical L shell photoionisation cross-section values.

Production of Li subshell and M shell vacancies following inner-shell vacancy production

Abstract The probabilities for transfer of vacancies from the K shell to an L i Subshell ( η KL i ) and to the M shell (η KM ), and from the L i Subshell to the M shell ( η L i M ) are evaluated for elements with atomic numbers 18 ≤ Z ≤ 96 using the theoretical radiative transition rates of Scofield [Phys. Rev. A 9 (1974) 1041; At. Data Nucl. Data Tables 14 (1974) 121] and radiationless transition rates tabulated by Chen et al. [At Data Nucl. Data Tables 24 (1979) 13; Phys. Rev. A 21 (1980) 442]. The calculated vacancy transfer probabilities are least-squares fitted to polynomials to obtain analytical relations that represent these probabilities as a function of atomic number.

M shell X-ray production cross sections and fluorescence yields for the elements with 71 ≤ Z ≤ 92 using 5.96 keV photons

Abstract Total M X-ray production (XRP) cross sections for ten elements in the atomic number region 71 ≤ Z ≤ 92 were measured at 5.96 keV incident photon energy. The average M shell fluorescence yields 〈 ω M 〉 have also been computed using the present measured cross section values and the theoretical M shell photoionisation cross sections. The results are compared with theoretical values.

Measurements of K to L shell vacancy transfer probability for the elements 37 ≤ Z ≤ 42

Abstract The probabilities for vacancy transfer from K shell to L shell, η kl , are deduced for six elements in the atomic region 37 ≤ Z ≤ 42 by measuring the L X-ray yields from targets excited by 5.96 and 22.6 keV incident photons, i.e. below and above the K edge of the elements and using the theoretical K shell and L shell photoionisation cross-sections. The measured results are found to be in good agreement with those based on relativistic Dirac Hartree Slater (RDHS) calculations and the available semi-empirical values. The theoretical η KL values for the elements with 18 ≤ Z ≤ 96 are least-squares fitted to the fifth-order polynomial in atomic number ( Z ).

Inelastic scattering of 59.5 keV photons by elements with 13⩽Z⩽82

Abstract Inelastic scattering differential cross-sections for 59.5 keV photons at an angle of 121° have been measured in 18 elements with 13⩽ Z ⩽82. The measurements were performed using an annular source of 241 Am radioisotope as photon source and a planar Si(Li) detector. The measurements were performed under vacuum ∼10 −2 Torr. The contribution due to photons scattered from the surroundings was minimized by placing the target and annular source assembly in a Pb housing, and using a vacuum chamber made of glass lined inside with Pb. Thin targets have been used to minimize the contribution of multiple scattered photons to the inelastic scattered peak. The product of the intensity of incident photons, detector efficiency, and other geometrical factors was determined by measuring the K X-ray yields from targets of different elements with 30⩽ Z ⩽69 excited by the 59.5 keV photons from 241 Am source and from the knowledge of K X-ray fluorescence cross-sections. A calibrated 241 Am radioactive point source was also used for this purpose. The measured inelastic scattering cross-sections are found to be in good agreement with those calculated using the Klein–Nishina cross-section for Compton scattering by stationary free electrons and the nonrelativistic Hartree–Fock incoherent scattering function S ( x , Z ).

Evaluation of chemical composition and efficacy of Chinese propolis extract on Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans: An in vitro study

Background: Propolis as a natural remedy has maintained its popularity over long periods of time. The aim of this study was to determine the chemical composition in terms of total phenolic compounds and flavonoids present in Chinese propolis and to carry out an in vitro evaluation of its antimicrobial activity and the minimal inhibitory concentrations for Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa). Materials and Methods: From the ethanolic extract of propolis (EEP), total phenol content was determined by the Folin–Ciocalteau method, flavones and flavonols by the modified aluminum chloride colorimetric method, and flavanones by the 2.4-dinitrophenylhydrazine (2,4-DNP) method. Agar well diffusion assay was used to evaluate the antimicrobial potential of propolis against Pg and Aa. The minimum inhibitory concentration of propolis against the two bacteria was determined using serial tube dilution technique. Results: The total concentration of phenol in the EEP was 19.44%, flavones and flavonols 2.616%, and flavanones 16.176%. The inhibitory zone depicting antimicrobial activity ranged from 18 to 25 mm for Pg and from 12 to 14 mm for Aa. The concentration range of Chinese propolis that is sensitive to inhibit the growth of Pg was 0.1–0.0125 μg/ml and for Aa it was 0.1–0.025 μg/ml. Conclusion: These data suggest that Chinese propolis has potent antimicrobial activity against the two periodontopathogens, suggesting its possible use as a natural alternative to the widely used synthetic antibiotics for periodontal therapy.

L x-ray production cross sections in Th and U at 17.8, 25.8 and 46.9 keV photon energies

The L x-ray production (XRP) differential cross sections in Th and U have been measured at the 17.8 keV incident photon energy (E_L3<Einc<E_L2, ELi is the Li subshell ionization threshold) in an angular range 90°-160°, and at the 25.8 and 46.9 keV incident photon energies (E_L1<Einc<EK) at an angle of 130°. The measurements were performed using the energy dispersive x-ray fluorescence set-up in secondary excitation mode. In contrast to the findings of an earlier experiment (Sharma and Allawadhi 1999 J. Phys. B: At. Mol. Opt. Phys. 32 2343), the present measurements rule out the possibility of a strong angular dependence of differential cross sections for various L3 subshell x-rays following selective photoionization of the L3 subshell. Integral L XRP cross sections at the 17.8, 25.8 and 46.9 keV photon energies, deduced assuming isotropic emission of the L x-rays, are found to be in good agreement with those evaluated using the most reliable theoretical values of Li (i = 1,2,3) subshell photoionization cross sections, fluorescence yields, x-ray emission rates and Coster-Kronig transition probabilities.

Measurements of L to M shell vacancy transfer probabilities for the elements in the atomic region 70 ≤ Z ≤ 92

Abstract The probabilities for vacancy transfer from L to M shell, \ ghLM, are deduced for 15 elements in the atomic region 70 ≤ Z ≤ 92 by measuring the M X-ray yields from the targets excited by 5.96 and 22.6 keV incident photons, i.e. below and above the L-edge of the elements and using the theoretical L and M shell photoionisation cross-sections. These results are compared with the theoretical values based on the relativistic Dirac-Hartree-Slater (RDHS) and the nonrelativistic approximate Herman-Skillman (AHS) calculations. From the comparison, it is concluded that the onset of L1−L3M5 Coster-Kronig transition occurs at Z = 75 as predicted by the RDHS model based Coster-Kronig transition energy calculations.

Determination of the antibacterial activity of simvastatin against periodontal pathogens, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans: An in vitro study

Context and Objective: Statin treatment, apart from its hypolipidemic action has proven its antimicrobial activity by improving the survival rate of patients with severe systemic bacterial infections. Periodontitis is an inflammatory disorder of tooth supporting structures caused by a group of specific microorganisms. The objective of the present study was to determine the antimicrobial activity of pure simvastatin drug against the primary periodontal pathogens. Materials and Methods: Minimum inhibitory concentration (MIC) was determined against Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans using serial dilution method. Results: MIC of simvastatin against P. gingivalis was 2 μg/ml and A. actinomycetemcomitans was found to be <1 μg/ml which requires further dilutions to determine the exact value. Conclusions: Data suggests a potent antimicrobial activity of simvastatin against both A. actinomycetemcomitans and P gingivalis. Hence simvastatin can be prescribed as a dual action drug in patients with both hyperlipidemia and periodontal disease.

Effect of automobile exhaust on the distribution of trace elements and its modulation following Fe, Cu, and Zn supplementation

The effect of automobile exhaust on the distribution of trace elements with special reference to Pb and its modulation following Cu, Zn, and Fe supplementation, in mouse organs, has been studied using Energy Dispersive X-ray Fluorescence technique. Seven elements, namely K, Fe, Cu, Zn, Br, Rb, and Pb, were detected in all the organs. The maximum concentration of Pb was found in lungs followed by that in liver and kidney. The effect of automobile exhaust was found to be significant on the concentrations of Fe and Pb; their concentrations were found to increase in all the organs. However, the concentrations of Cu and Zn were found to be decreased significantly in the liver. In the animals given Fe, Cu, or Zn supplementation along with motor exhaust, the percentage change in the concentration of Pb in lungs was decreased, and that of Fe was increased significantly. In kidney, no significant change was observed for the animals given Cu and Zn, whereas for animals given Fe, the level of Pb decreased significantly. In liver, the reduction in the level of Zn in the exhaustexposed animals was made up and the level of Pb was reduced following Zn supplementation. These results clearly indicate that Fe and Zn play an important role in Pb metabolism and tend to lower the absorption of Pb. The effect of Fe is more pronounced than that of Zn, whereas the effect of Cu seems to be insignificant.