Cluster decays of Ba nuclei are calculated within a preformed cluster model. The n-nuclei H, Be, C, 0, and Ne are predicted as the possible decay modes, lying within the limits of present experimental methods. Other than the o. particle, C decay of Ba is shown to be the most probable one with half-life time T&(2 10 s, stressing the role of doubly magic 50Sn daughter nucleus in cluster radioactivity. The use of di8'erent Q values for Ti12 estimates and presence of nuclear structure efFects in Geiger-Nuttall plots are also discussed. PACS number(s): 23.60.+e, 21.60.Gx, 23.90.+w, 27.60. +j Recently, one of us and collaborators  have pointed out some new instabilities against exotic cluster decays for some "stable" nuclei in the region 50 ( Z ( 82. In particular, C and 0 decays of Ba are predicted to have half-life times 102 and 10 s, respectively, which are well below the presently measured upper limit for heavy cluster decays of radioactive nuclei. However, 2 Ba is a short lived nucleus with the measured  half-
Cluster decays of the neutron-deficient Xe, Ba, Ce, Nd, Sm, and Gd parents are studied within the preformed cluster model of Malik and Gupta. The calculated preformation probabilities (Pa) and decay half-lives show that the a-nuclei (A2 --4n, Zq --N2) clusters, like Be, C, 0, Ne, Mg, and Si, emitted from N = Z parents are the most probable cases for measurements. Many of these clusters are shown to be within the upper limit of present experimental methods. This stresses the importance of 50 Sn-daughter in these decays.The fact that A2 --4n cluster decays are more probable than A2 --4n+2 clusters demonstrates that Sn radioactivity is associated with A2 --4n, Zq = N2 (o-nuclei) clusters. Structure effects of the nuclear (proximity) potential and binding energies (the shell effects) in GN plots and in variation of Po with the parent mass A are also pointed out.PACS number(s): 23.60.+e, 27.60. +j, 23.90.+w, 21.60.Gx
The aim of this study was to investigate the major chemical compositions of the chloroform extract of lichen Parmelia erumpens from Western Ghats, Kerala, India and its antimicrobial and anticancer activities. Chloroform extract was purified by silica gel column chromatography to obtain three major compounds and their chemical structures were characterized by 1 H-NMR, 13 C-NMR, UV and HR-MS spectroscopic methods as atranorin (1), (+)-usnic acid (2) and 2-hydroxy-4-methoxy-3,6dimethylbenzoic acid (3). The minimal inhibitory concentration (MIC) by the broth micro dilution and agar disc diffusion methods was used to record the antimicrobial activity. Out of three compounds tested, 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid recorded excellent antimicrobial activity especially against medically important bacteria and fungi and the MIC values ranged from 0.06 to 4 mg ml À1 against test bacteria and 0.12 to 16 mg ml À1 against test fungi. The best MIC of 0.06 mg ml À1 by 2hydroxy-4-methoxy-3,6-dimethylbenzoic acid was recorded against Vibrio cholera, a human pathogenic bacterium responsible for causing life threatening diseases like profuse watery diarrhea. Anti cancer activity was initially screened by MTT assay in A549, B16F10, Caski and HepG2 cell lines. MTT assay results showed that the growth of cancer cells was suppressed by 2-hydroxy-4-methoxy-3,6dimethylbenzoic acid in both dose-and time-dependent manners. A549, B16F10 and Caski cells treated with 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid showed typical apoptotic morphology when stained with acridine orange-ethidium bromide and hoechst staining. Cell cycle analysis clearly indicated that cell death was due to apoptosis. Enhancement in the proliferation of lymphocytes suggested immunomodulatory activity of this compound. To our best knowledge anticancer activity of 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid was reported here for the first time. Thus the results of the present study suggest that 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid has a strong potential to be developed as an antimicrobial and anticancer drug target after further clinical evaluation.
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