Shofiur Rahman

Assessment of indoor radon doses received by the students in the Azad Kashmir schools, Pakistan.

Several epidemiological studies conducted on thousands of underground miners suggest that long- term exposure to high radon concentration can increase the risk of lung cancer. Keeping in view the importance of the subject, numerous studies throughout the world have been carried out to measure indoor radon concentration and its resulting doses at occupational and non-occupational sites. The purpose of the current study was to measure indoor radon concentration and its resulting doses received by the students of Azad Kashmir government schools. For this purpose, CR-39 radon detectors were installed in 80 carefully selected schools. The detectors were placed at a height of 3-5 ft. (depending upon average height of students in particular class) from the ground. After exposure of 90 d detectors were etched for 9 h in 6 M NaOH at 70°C and the observed track densities were related to radon concentrations. The measured indoor radon concentration ranged from 22 ± 9 to 228 ± 3 Bq m(-3) with a mean value of 78 ± 5 Bq m(-3). Based on the measured indoor radon data, the annual effective doses were found to vary from 0.55 ± 0.04 to 0.71 ± 0.03 mSv y(-1). The overall mean effective dose for the studied area was found to be 0.63 ± 0.04 mSv y(-1). Reported values for radon concentrations and corresponding doses are lower than ICRP recommended limits for workplaces.

Radiation Doses Due to Indoor Radon Exposure, Before and After the 2005 Earthquake, in Dwellings of Muzaffarabad and the Jhelum Valley, Azad Kashmir, Pakistan

Radiation doses from indoor radon exposure, before and after the 2005 earthquake, have been assessed from measurements taken in the city of Muzaffarabad and Jhelum valley, Azad Kashmir, Pakistan. Indoor radon concentration was measured in dwellings in Muzaffarabad city and the Jhelum valley after the devastating 2005 earthquake using CR-39 based radon box type detectors which were exposed to indoor radon for 60 days. After processing, the observed track densities were related to the indoor radon concentrations using a calibration factor of 0.0092 tracks cm-2 · hr-1 = 1 Bq m-3 of 222 Rn and compared with already published data obtained before the earthquake. The post-earthquake weighted average indoor radon concentration ranged from 65 Bq m-3 to 398 Bq m-3 for the dwellings of state capital city of Azad Kashmir where pre-earthquake values were in the range of 89 Bq m-3 to 167 Bq m-3. In the Jhelum valley, post-earthquake indoor radon concentrations varied from 81 to 509 Bq m-3 and 64 to 456 Bq m-3 in the bedrooms and kitchens, respectively while pre-earthquake radon concentration for Jhelum valley ranges from 86 to 236 Bq m-3 and 62 to 208 Bq m-3 in the bedrooms and kitchens, respectively. The post earthquake indoor radon concentration levels and hence radiation doses have been found higher than those of pre-earthquake values.

Radiological hazards due to naturally occurring radionuclides in the selected building materials used for the construction of dwellings in four districts of the Punjab Province, Pakistan.

This paper presents the finding of a study undertaken to determine the naturally occurring radionuclides present in commonly used building materials for dwellings and workplaces in four districts of the Punjab Province, Pakistan. The concentrations of (226)Ra, (232)Th and (40)K were measured by using gamma-ray spectroscopy. A total of 80 samples of building materials were collected from various manufacturers and suppliers of the studied area. The specific activities of (226)Ra, (232)Th and (40)K were measured in building samples, and results ranged from minimum values of 9 ± 1, 9 ± 2 and 27 ± 8 Bq kg(-1) to maximum values of 106 ± 5, 133 ± 5 and 914 ± 21 Bq kg(-1) with mean values of 42 ± 3, 48 ± 3 and 376 ± 16 Bq kg(-1), respectively. From the measured activity concentrations, equivalent radium (Ra(eq)), terrestrial absorbed dose rate, annual effective dose as well as external and internal hazard indices were calculated and found to range from 52 ± 7 to 274 ± 15 Bq kg(-1), 23 ± 3 to 130 6 nGy h(-1), 0.15 ± 0.02 to 0.80 ± 0.03 mSv, 0.14 ± 0.02 to 0.75 ± 0.04 and 0.2 ± 0.02 to 0.98 ± 0.05, respectively. These results were comparable to the results of similar studies undertaken locally and in other countries. The samples considered were safe for use in construction of dwellings in the study area and do not pose any significant source of radiation hazard.

Assessment of Seasonal Variation of Indoor Radon Level in Dwellings of Some Districts of Azad Kashmir, Pakistan

Measurements of indoor radon concentrations in 200 dwellings of four districts of Azad Kashmir have been carried out using CR-39-based radon dosimeters. Indoor radon levels were calculated for four seasons (i.e. spring, summer, autumn and winter) in Muzaffarabad, Hattian, Neelum and Poonch districts. Maximum value of radon concentration (398 ± 2 Bq·m-3) has been found in Muzaffarabad district (in bedrooms) and minimum value (23 ± 9 Bq·m -3) is reported for Hattian district (in living rooms). Elevated values of radon levels have been found in winter, whilst lower values are observed in summer season. Seasonal correction factors calculated for spring, summer, autumn and winter seasons were found to be 1.02 ± 0.91, 0.86 ± 0.77, 0.98 ± 0.92 and 1.14 ± 1.04, respectively. Measured values for winter/spring, winter/summer and winter/autumn radon ratios were found as 1.11 ± 1.28, 1.33 ± 1.21 and 1.15 ± 1.17. Radon doses have been calculated and yearly mean effective dose has been found 2.52 ± 1.22 mSv, which is less than the lower limit of the recommended action level 3—10 mSv.

The Thyroxine-Containing Thyroglobulin Peptide (aa 2549–2560) Is a Target Epitope in Iodide-Accelerated Spontaneous Autoimmune Thyroiditis

Enhanced iodide ingestion is known to accelerate the incidence and severity of spontaneous autoimmune thyroiditis [iodide-accelerated spontaneous autoimmune thyroiditis (ISAT)] in NOD.H2h4 mice. CD4+ cells are required for the development and maintenance of ISAT, but their target epitopes remain unknown. In this study, we show that the previously identified thyroglobulin (Tg) T cell epitope p2549–2560 containing thyroxine at position 2553 (T4p2553) induces thyroiditis as well as strong specific T and B cell responses in NOD.H2h4 mice. In ISAT, activated CD4+ T cells specific for T4p2553 are detected before the disease onset in thyroid-draining cervical lymph nodes only in mice placed on an iodide-rich diet and not in age-matched controls. In addition, selective enrichment of CD4+ IFN-γ+ T4p2553-specific cells is observed among cervical lymph node cells and intrathyroidal lymphocytes. T4p2553 was equally detectable on dendritic cells obtained ex vivo from cervical lymph node cells of NaI-fed or control mice, suggesting that the iodide-rich diet contributes to the activation of autoreactive cells rather than the generation of the autoantigenic epitope. Furthermore, spontaneous T4p2553-specific IgG are not detectable within the strong Tg-specific autoantibody response. To our knowledge, these data identify for the first time a Tg T cell epitope as a spontaneous target in ISAT.

Synthesis, structural properties, electrophilic substitution reactions and DFT computational studies of calix[3]benzofurans

Calix[3]benzofurans have been synthesized by a modified TosMIC coupling reaction, followed by acid treatment and an intramolecular cyclization reaction with TMSI (trimethylsilyl iodide); X-ray analysis established the structures of two samples, both showing a cone conformation. 1H NMR spectroscopic analyses of the calix[3]benzofurans reveal that they can adopt drastically different conformations in solution and undergo very fast conformational changes relative to the NMR time scale. Calix[3]benzofuran 4a exists as two conformers, namely the cone and saddle forms, in a ratio of 83 : 17 at −50 °C. A series of calix[3]benzofuran derivatives was synthesized by electrophilic aromatic substitutions, such as bromination, formylation and acylation, to investigate the influence of the substituents on the conformations of the calix[3]benzofurans. 1H NMR spectral analyses of the acyl derivatives at room temperature indicated that these macrocycles exist as a mixture of two isomers that are slowly interconverted on the 1H NMR timescale. The conformational isomers of the calix[3]benzofurans and their derivatives obtained from DFT methods (based on the crystal structure analysis results) were used to estimate the total energies of the different conformations.

Naphthyl “capped” triazole-linked calix[4]arene hosts as fluorescent chemosensors towards Fe3+ and Hg2+: an experimental and DFT computational study

Four new naphthyl “capped” 1,2,3-triazole-linked receptors 6a–d have been synthesized and characterized. Their binding properties towards different metal ions have been studied by 1H NMR and fluorescence spectroscopy and the association constants were analysed by a non-linear global fit method. The fluorescent spectral changes show that 6a–d are sensitive and selective towards Fe3+ and Hg2+ ions. DFT calculations of the binding modes of 6a–d with these metal ions are also presented.

Supramolecular host–guest complexation of Lash's calix[4]azulene with tetraalkylammonium halides and tetrafluoroborate salts: binding and DFT computational studies

Calix[4]azulene 1 is shown to be an effective molecular receptor for tetraalkylammonium halide and BF4− salts. The respective binding constants were determined using global-fit analyses of the spectral data from UV-vis absorption titration studies. A DFT study of the putative complexes formed with 1, and the X-ray structure of 1 itself is also reported.

Synthesis and evaluation of a novel ionophore based on a thiacalix[4]arene derivative bearing imidazole units

O-Alkylation of the flexible thiacalix[4]arene 1 with 2-chloromethyl-1-methyl-1H-imidazole 2 in the presence of Na2CO3 or K2CO3 afforded mono-O-alkylation product 3 in 29–51% yield, along with recovery of the starting compound. In contrast, the same reaction in the presence of Cs2CO3 gave only one pure stereoisomer, namely 1,3-alternate-4; other possible isomers were not observed. Alkali metal salts such as Na2CO3 and Cs2CO3 can play an important role in the conformer distribution via a template effect. The conformations of the receptors, mono-O-alkylation product 3 and that of 1,3-alternate-4, have been confirmed by X-ray crystallography. Furthermore, the complexation properties of the receptor 1,3-alternate-4 toward selected alkali/transition metal cations are reported. The two-phase solvent extraction data indicated that 1,3-alternate-4 exhibited a stronger extraction efficiency for transition metals over alkali metals. The dichromate anion extraction ability of 1,3-alternate-4 showed that it could serve as an efficient extractor of HCr2O7−/Cr2O72− anions at low pH.

Synthesis of a cone-conformer bimodal calix[4]arene-crown-5 which forms a sensitive cesium ion sensing layer on gold-coated microcantilevers

A “bimodal” or upper- and lower-rim functionalized “calix-crown-5” reported herein was unexpectedly formed preferentially in a cone conformation. This was confirmed both by NMR spectroscopy and by single-crystal X-ray crystallography. The thioacetate functionalities on the new calix-crown-5 enabled it to form stable SAMs on the Au surface of a microcantilever, and a sensitive cesium ion sensor.