The fast reaction technique of pulse radiolysis in conjunction with UV- visible absorption detection was used to determine the rate of reactions of hydrated electron, hydrogen atom, hydroxyl radical and dichloride anion radical with tetraammineplatinum(II) perchlorate and with trans- dihydroxotetraammineplatinum(IV) perchlorate complexes. Generally these reactions proceed at near diffusion-controlled rates. The second-order rate constant for the reaction of e
, H, OH and Cl
radical with the Pt(II) complex are (1.9±0.1)·1010 M–1·s–1, (2.8±0.3)·1010 M–1·s–1, (6.6±0.4)·109 M–1·s–1 and (9±1)·109 M–1·s–1, respectively. The rate constant for the reaction of e
with the Pt(IV) complex is (4.9±0.3)·1010 M–1·s–1, however, H atom and OH radical reactions proceed at relatively slower rates.
Aqueous solution of rose bengal dye has been studied spectrophotometrically as a gamma-ray dosimeter for the measurement of
low doses of radiation. The useful dose range was found to be from 50 to 1000 Gy when the measurements were made at 549 nm.
The effects of temperature and light conditions on the stability of response during post-irradiation storage were also investigated.
When stored in dark at room temperature, the dosimetric solutions showed a stable response up to 22 days. The storage of irradiated
solutions in diffused sunlight showed a stable response only up to 6 days. When exposed to direct sunlight, very prominent
and fast bleaching of dye solution occurred. At low storage temperature (ca. 11 °C), dosimetric response was found to be stable
up to 22 days while at higher temperature (ca. 30 °C), the response of dosimetric solution was stable only up to 6 days. The
rose bengal aqueous solution showed promising characteristics as a low dose radiation dosimeter when stored at lower temperatures
(<25 °C) in dark.
Five spices, cumin, coriander, clove, cinnamon and black pepper were irradiated by gamma-ray doses of 1.0 and 5.0 kGy and
thermoluminescence (TL) method was used for identification of the irradiation treatment. The TL response of the minerals isolated
from irradiated samples was much higher as compared to the mineral particles from unirradiated control samples. For the normalisation
of results the separated minerals were reirradiated to a normalisation dose of 1.0 kGy and the TL glow curve was recorded
a second time. By comparing the glow curves of irradiated and unirradiated samples, finding the ratio of the areas of first
and second glow curves (TL1/TL2) and comparing the shapes of the glow curves, all the irradiated and unirradiated samples were identified correctly.
Authors:Hasan Khan, Shagufta Naz, and Safia Tabassum
Aqueous solution of crystal violet has been evaluated spectrophotometrically as a gamma-ray chemical dosimeter. The response
of the chemical dosimetric system has also been investigated under different environmental conditions, such as light and temperature.
In the present study the response has been measured at two wavelengths; 588 nm (λmax of the irradiated solution) and 500 nm. The response of the crystal violet dosimeter was linear in the dose range of 50–550 Gy
at pH 5.6 when absorption measurements were made at 588 and 500 nm. The response of the crystal violet dosimeter during post-irradiation
storage at room temperature in dark showed slight decrease in absorbance at 588 and 510 nm but the response was almost stable
at 460 nm. For higher doses, the change in the response was greater as compared to the low doses. Post-irradiation stability
during diffused sunlight showed significant decrease in the response for higher dose at 588 and 510 nm and slower decrease
in the response for lower dose at the above mentioned wavelengths. However the response was almost stable up to 97 days at
460 nm for higher and lower doses. At 4 °C, the decrease in the absorbance was slower at 588 and 510 nm while the response
was almost constant at 460 nm. At higher temperatures, such as 40 °C, the decrease in the absorbance was greater at 588 and
510 nm while at 460 nm the absorbance was almost constant for about 3 months.
Authors:Hasan Khan, Gulzar Ahmad, A. Sattar, and S. Durrani
Some plastic sheets manufactured or commercially available in Pakistan have been tested as radiation dosimeters for cobalt-60 -rays. Radiation induced colouration in the plastics have been measured spectrophotometrically. The results show that 2 mm thick clear poly(methyl methacrylate) (PMMA) can be used as radiation dosimeter up to 45 kGy when absorption measurements are made at 305 nm and 314 nm; whereas 1 mm thick clear poly(vinylchloride) (PVC) is useful up to 30 kGy when measured at 396 nm. The response of PMMA dosimeter is stable for at least 15 days and that for PVC for 30 days, when stored under ambient conditions after irradiation. Post-irradiation stability at various temperatures (–10 to 55°C) has also been studied.
Authors:Fatema Moni Chowdhury, Mohammed Ziaur Rahman, Md Murshed Hasan Sarkar, Fazle Rabbi, Sirajul Islam Khan, Chowdhury Rafiqul Ahsan, and Nils-Kåre Birkeland
Recently, we reported the induction of protective immunity by environmental Escherichia albertii strain DM104 against Shigella dysenteriae in guinea pig model. In this study, we assessed three different immunization routes, such as intranasal, oral, and intrarectal routes, and revealed differences in immune responses by measuring both the serum IgG and mucosal IgA antibody titers. Protective efficacy of different routes of immunization was also determined by challenging immunized guinea pigs against live S. dysenteriae. It was found that intranasal immunization showed promising results in terms of antibody response and protective efficacy. All these results reconfirm our previous findings and additionally point out that the intranasal immunization of the environmental E. albertii strain DM104 in guinea pig model can be a better live vaccine candidate against shigellosis.