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We have deduced that bulk viscous Bianchi type I barotropic fluid cosmological model with varying $\Lambda$ and functional relation on hubble parameter by solving the field equations bimetric theory of gravitation. It is observed that our model has exponentially accelerating expansion at late time starting with decelerating expansion which agreed the observation of Perlmutter (1998), Knop (2003), Tegmark (2004) and Spergel (2006). In the beginning, our model has more than three spatial-dimensions then it switched over to three-dimensional spatial geometry at late epoch of time and it is agreed with Borkar et al. (2013). Other geometrical and physical behavior of the model have been studied.

The paper presents the dosimetric characterization of lithium calcium aluminum fluoride doped with europium and yttrium (LiCaAlF 6 :Eu,Y), synthesized by simple melt process. The characterization involved thermoluminescence (TL), optically stimulated luminescence (OSL), photoluminescence (PL) spectra, OSL emission spectra, minimum measurable dose, fading, dose response and photon energy dependence measurements. The OSL sensitivity of this phosphor to ionizing radiation was found to be ∼20 times to that of commercially available Al 2 O 3 :C, whereas, the TL sensitivity was ∼2.5 times to that of CaSO 4 :Dy (0.05 mol%). Photoluminescence (PL) and OSL emission spectra suggest that the Eu 2+ ions are responsible for OSL emission. The reusability of OSL discs for 50 cycles for a test dose of 20 mGy has been established. Minimum detectable dose for the phosphor in continuous wave OSL (CW-OSL) mode was found to be 0.5 μGy with negligible fading post 9 days of irradiation. Owing to its excellent dosimetric characteristics the phosphor is a highly sensitive dosimetric grade phosphor and is a serious contender for various radiological applications.

K2Ca2(SO4)3:Eu nanophosphor was synthesized by chemical coprecipitation method and annealed at different temperatures from 400 to 900 °C. The nanophosphor annealed at 600 °C showed cubic structure with crystallite size ~25 nm. TEM shows morphology of K2Ca2(SO4)3:Eu nanophosphor was in the form of nanorods having diameter ~20 nm and length of ~100–200 nm. These samples were irradiated with gamma radiation for the doses varying from 10 mGy to 10 kGy and their Thermoluminescence (TL) and continuous-wave optically stimulated luminescence (CW-OSL) have been studied. CW-OSL response was found to be maximal for the sample annealed at 600 °C. The TL glow curve of the nanophosphor apparently showed a major peak at around 160 °C accompanied by three low intensity peaks at ~75, 215 and 285 °C. The traps responsible for all the TL peaks in K2Ca2(SO4)3:Eu were also found to be OSL sensitive. The qualitative correlation between TL peaks and CW-OSL response suggested that the traps associated with low temperature peaks are responsible for fast decay and the traps associated with the higher temperature peaks are responsible for slow decay of the OSL signal. OSL response showed linear behavior up to 1 kGy and saturated with further increase in the gamma dose. The wide OSL response makes studied K2Ca2(SO4)3:Eu nanophosphor a good candidate for high dose measurement.

The culmination of Continuous Wave OSL (CW-OSL) acquisition after initial few seconds offers improvement in dose detection threshold for Al 2 O 3 :C. Consequently, the traps from which dose information can be retrieved are still occupied by charge carriers and therefore can be stimulated multiple number of times for extracting OSL signal. This offers an approach for reassessment of the dose in an inadvertent circumstance of dose information being lost. Calibration tables and curves are generated for different stimulation intensities (ranging from 32 to 72 mW/cm 2 ) and signal integration times (ranging from 1 to 10 s) that can be used for re-estimation of the doses lying in the range of 1 mGy to 1 Gy. The qualitative as well as quantitative analysis of the observed trends with respect to stimulation intensity and signal integration time is carried out. The behaviour of dose response curves for successive readout numbers is also studied.

A new Cu,P-doped, sodium fluorosilicate-based optically stimulated luminescence (OSL) phosphor is developed. This phosphor shows good OSL properties, and the sensitivity is comparable with that of the commercial Al(2)O(3):C (Landauer, Inc.) phosphor. For the luminescence averaged over initial 1 s, blue-stimulated luminescence and green-stimulated luminescence sensitivities were found to be 0.76 and 3.8 times, respectively, of Al(2)O(3):C (Landauer, Inc.) with 28 % of post-irradiation fading in 3 days and nil thereafter. The simple preparation procedure, fast decay, very good sensitivity and moderate fading will make this phosphor suitable for radiation dosimetry, using OSL.

OSL and TL in some Cu doped alkali fluoro-silicates were studied. These investigations show that the materials possess good OSL properties and the sensitivity is comparable to that of the commercial α-Al 2 O 3 :C phosphor. Of the several fluoro-silicate phosphors studied Cu doped Na 2 SiF 6 is found to be highly sensitive. The initial OSL intensity averaged over first second using blue and green light stimulation, were found to be 1.2 and 13.3 times respectively of Al 2 O 3 :C. The simple preparation procedure, high OSL sensitivity, fast decay, and high photoionization cross-section will make these phosphors suitable for on-line radiation dosimetry, particularly in medical dosimetry applications.

Cu + was doped in fused quartz using simple technique and the BSL/IRSL and TL studies were carried out. The Cu + doped quartz shows enhanced TL as well as OSL sensitivity compared to the undoped material. The OSL sensitivity with blue stimulation, in particular, is relatively high, about 13% of the commercially used OSL phosphor (Al 2 O 3 :C-Landauer Inc.) on the basis of initial OSL intensity measurements (i.e. luminescence averaged over first 3 s). Earlier works show that OSL/TL signals in natural quartz is stable and thus can be used in archeological dating and other dosimetric applications. The aim of the present study is to investigate TL/OSL characteristics of Cu + doped fused quartz.