Dosimetric studies and chemical kinetics of Resazurin dye and its possible use as radiation dosimeter

Journal of Radioanalytical and Nuclear Chemistry - The structural and optical properties of the neutron irradiated PMMA doped by 5 wt% RhB have been investigated. Fourier transform infrared...     

Human hair as a pollutant dosimeter

Human hair has been proved to be a better dosimeter than even blood for tracing most of the heavy metal toxins when they penetrate the biosphere. The high precision of the neutron activation analysis (NAA) enabled researchers to elegantly differentiate between endogenous and exogenous contamination and to thoroughly study poisonings caused by these physiologically-unimportant elements. An extensive amount of bench-scale work has been accomplished in these laboratories to show the capacity of INAA to detect the presence of 10 nuclides (or more) with a precision of about 5%. The principal objective of the present study was to employ this assaying power and the tendency of scalp hair to uptake metals from aqueous solutions, to design an adsorption system which can easily be used by the waste-management people who are searching for a cost-effective technique to monitor and remove these pollutants from relatively large volumes of industrial effluents.     

The minimum range of dose measurement on polyethylene film dosimeter

Polyethylene dosifilm for ⁶⁰Co γ-ray and electron beam have been investigated. The dose response of PE film irradiated by electron beam on 5–600 kGy. The slope of curves is 3.488 × 10^-2, the total uncertainty of experiment lower than 10%, the reproductivity of PE film irradiated by γ-ray was better than EB irradiated. There was an inflection point around 55 kGy in γ-ray irradiated case, so the slope is different (i.e. 4.4 × 10^-2). The influence of oxygen and interface were compared and discussed.     

‘Extremely diluted solutions’ as multi-variable systems

A large number of thermodynamic and transport measurements were conducted on ‘extremely diluted solutions’ (EDS). The physico-chemical results presented here allow us to hypothesize that the process of iterated dilutions and succussions is capable of modifying in a permanent way the features of water. A really intriguing phenomenon was the evolution of two physico-chemical properties with time. The calorimetric and conductometric measures were carried out as a function of the age of the samples. We found a good linear correlation between these two independent parameters, also as a function of time. A careful study of the phenomenon puts in evidence that these solutions are characterised by multiple independent variables. The EDS behave as complex systems, influenced by peculiar aspects of the preparation technique and also by the storage conditions. The EDS are far-from-equilibrium systems, capable of auto-organising themselves as a consequence of little perturbations.     

Styrylcyanine dye solutions for radiation dosimetry

The effect of -radiation on the electronic absorption spectra of the negatively solvatochromic dyestuff1, namely, 4-(4-N,N,-dimethylaminostyryl)-pyridinium methiodide in water and dimethylsulphoxide solvents is investigated. Ionizing radiation at different absorbed doses brought about gradual bleaching of aerated dye solutions. The -radiation-induced degradation and the consequent changes in the electronic absorption spectrum of dye 1 are discussed in the light of the theoretically calculated spectrum. The linear response range of dye1 in case of DMSO solution is wider than that in H₂O. The results demonstrate that the radiochromic dye solution offer dosimetry in the low dose range by means of visible spectrophotometric analysis.     

Aqueous phenylacetic acid as a low-dose fluorescence dosimeter

Total fluorescence of aqueous phenylacetic acid system at neutral pH has been evaluated as low-dose -ray chemical dosimeter, using the fluorescence accessory of a UV-Vis spectrophotometer. The useful working range of the system is from 4 to 70 Gy. The postirradiation stability of the dosimeter response has been studied at different pH's, storage temperatures and light conditions. The post-irradiation stability of the dosimeter decreases with an increase in storage temperature. The stability is not affected in diffuse sunlight but it is very unstable in direct sunlight.     

Thermodynamics of surfactant-dye complex formation in aqueous solutions. Sodium alkyl sulfates and azo oil dye systems

Thermodynamics of surfactant-dye complex formation have been studied, in terms of equilibrium coefficient, using a spectrophotometer. The systems are 6 sodium alkyl sulfates, which have different alkyl chain lengths, and 4-phenylazo-1-naphthylamine. A pronounced spectral change in the dye solution occurs on addition of the surfactant; the change has a definite isosbestic point and a new absorption band at 535 nm because of surfactant-dye complex formation, which is caused by hydrophilic-hydrophilic interaction. As the alkyl chain length in the surfactant increases, the values of free energy change (negative) increase, while the value of enthalpy change (negative) increases and the value of entropy change (positive) decreases. The longer the alkyl chain length in surfactant increase, the more stable the surfactant-dye complex becomes.Surfactant-dye complex will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.     

Ethanol/water solutions as certified reference materials for breath alcohol analyzer calibration

The Federal Institute for Materials Research and Testing (BAM), Germany, has issued a series of large volume ethanol in water certified reference materials (CRMs), primarily developed for the calibration of evidential breath alcohol analyzers in Germany. The certified parameter is the ethanol mass concentration at 20 °C. When used in a wet bath simulator, the solutions deliver gas samples that meet the requirements set by the Organization of Legal Metrology for calibration of breathalyzers. The materials were prepared gravimetrically by spiking of ethanol into water in single 5 L units. A complete uncertainty budget for the preparation process has been established. The purity of the commercial ethanol stock solution was identified to be the main source of uncertainty. For stability and homogeneity measurements and for the verification of the gravimetric mass concentration of the CRMs, a robust high-precision gas chromatography, with flame-ionization detection method for ethanol determination in aqueous samples was developed and validated. The good performance of this method has been demonstrated in several international comparisons organized by the Consultative Committee for Amount of Substance—Metrology in Chemistry at the International Bureau of Weights and Measures.     

DNA as a solar dosimeter in the ocean.

Stratospheric ozone depletion may result in increased solar UV-B radiation to the ocean's upper layers and may cause deleterious effects on marine organisms. The primary UV-B damage induced in biological systems is to DNA. While physical measurements of solar UV-B penetration into the sea have been made, the effective depth and magnitude of actual DNA damage have not been determined. In the experiments reported here, UV-B-induced photoproducts (cyclobutane pyrimidine dimers) have been quantified in DNA molecules exposed to solar UV at the surface and at various depths in clear, tropical marine waters off Lee Stocking Island (23 degrees 45' N, 76 degrees 0.7' W), Exuma Cays, Bahamas. (14C)thymidine-labeled DNA or unlabeled bacteriophage phi X174 DNA was placed in specially designed quartz tubes at various depths for up to five days. Following exposure, DNA samples were removed to the laboratory where UV-B-induced pyrimidine dimers were quantified using a radiochromatographic assay, and bacteriophage DNA inactivation by solar UV-B was assayed by plaque formation in spheroplasts of Escherichia coli. Pyrimidine dimer induction was linear with time but the accumulation of dimers in DNA with time varied greatly with depth. Attenuation of dimer formation with depth of water was exponential. DNA at 3 m depth had only 17% of the pyrimidine dimers found at the surface. Bacteriophage phi X174 DNA, while reduced 96% in plaque-forming ability by a one day exposure to solar UV at the surface of the water, showed no effect on plaque formation after a similar exposure at 3 m. The data collected at the water's surface showed a "surface-enhanced dose" in that DNA damages at the real surface were greater than at the imaginary surface, which was obtained by extrapolating the data at depth to the surface. These results show the sensitivity of both the biochemical (dimers) and biological (phage plaques) DNA dosimeters. DNA dosimeters offer a sensitive, convenient and relatively inexpensive monitoring system, having both biochemical and biological endpoints for monitoring the biologically effective UV-B flux in the marine environment. Unlike physical dosimeters, DNA dosimeters do not have to be adjusted for biological effectiveness since they are sensitive only to DNA-mediated biologically effective UV-B radiation. Results of pyrimidine dimer induction in DNA by solar UV accurately predicted UV doses to the phage DNA.     

Rotational-diffusion anomalies in dye solutions from transient-dichroism experiments

Subnanosecond transient-dichroism experiments have been performed to investigate the rotational diffusion of dyes in solution. Dyes and solvents were chosen in a way to obtain information on the influence of size, shape and hydrogen-bonding abilities either of the solute or the solvent molecules. One finds slow orientational relaxation of di-anionic xanthene dyes in alcohols, while oblate cationic dyes rotate faster in spite of their comparable size. The rotational diffusion times for alcohol solutions exceed the theoretical values predicted by the Debye-Einstein model except for prolate molecules. For a solute molecule with internal mobility the rotational diffusion exhibits a partial slip behaviour. It is shown that the deviations from the Debye-Einstein model are restricted to alcohols since for other solvents either with or without strong hydrogen-bonding abilities the experimental values agree with the hydrodynamic model including the stick-boundary condition. Experiments on erythrosine B reveal the influence of size and shape of the attached solvent molecules.     

Gamma radiolysis of erythrosine dye in aqueous solutions

Beryllium-7, mainly measured via γ-spectrometry, is used as a (natural) radiotracer for education and science. For activities?<?0.1 Bq and samples containing also longer-lived ¹⁰Be, accelerator mass spectrometry (AMS) is the method-of-choice. We demonstrate that ⁷Be and ¹⁰Be can be quantified at the Dresden AMS facility on the same prepared BeO. Detection limits (⁷Be) are?~?0.6 mBq. Samples as small as tens of millilitres of rainwater can be chemically processed (after acidification) within a few hours without expensive and slow ion exchange. Isobar (⁷Li) suppression by chemistry and AMS is sufficient to guarantee for an ultrasensitive, cheap, and fast detection method for ⁷Be allowing high sample throughput.

     

MOSFET with a boron-loaded gate as a low-energy neutron dosimeter

A MOSFET-based low-energy neutron dosimeter has been fabricated using a ¹⁰B loaded gate electrode as (n,α) converter. The response to thermal neutrons has been studied.     

The effect of humidity on the accuracy of measurement of an electret radon dosimeter

Test has been conducted for the response of electret radon dosimeters with varying levels of humidity. At a constant value of radon concentration, measured values have been found to increase linearly with increasing humidity, from 30% RH up to a value of 85% RH. On this basis we argue for the establishment of a humidity-dependent calibration factor.     

The photoacoustic determination of fluorescence yields of dye solutions

A new method for the measurement of the primary fluorescence quantum yield of dye solutions is presented. The method is conceptually and experimentally simple, relying of the S_n → S₁ transition probability as an internal standard for comparison with the S₁ radiationless transition probability, both probabilities being measured by photoacoustic spectroscopy.     

Photo-induced electron transfer in surfactant solutions containing thionine dye

The mechanism of photovoltage generation in the micellar solution of nonionic surfactants incorporating thionine dye involves charge-transfer (CT) or electron donor acceptor (EDA) interaction; the dye acts as the electron acceptor and the surfactants act as the electron donors. This is well corroborated by the spectral studies of the systems. The thermodynamic and spectral properties of the complexes are presented. The photovoltage generation, the spectral shifts due to complexation, and the thermodynamic properties of the complexes are found to be well correlated.     

Thermodynamics of surfactant-dye complex formation in aqueous solutions II. Sodium dodecyl sulfate and some azo oil dye systems

Spectrophotometric and thermodynamic investigations are reported of the interactions between anionic surfactant (sodium dodecyl sulfate) and six azo oil dyes (benzene azo naphthalene type) which have an amino group at 4-position of naphthalene. A pronounced spectral change in the dye solution occurs on addition of surfactant. For increasingly surfactant concentrations (below the CMC), the interaction between dye and surfactant is so sharp that the systems may be said to exhibit an isosbestic point; then a new absorption band appears at longer wavelengths. The spectral data can be quantitatively interpreted in terms of a complex formation. The equilibrium coefficients of the complex formation are determined at different temperatures. The thermodynamic parameters of the complex formations (the free energy change (G), enthalpy change (H) and change in entropy (S) are also calculated. The reaction of complex formation is exothermic (H negative).G is dependent on the hydrophobic nature andpKa of the dye. These complexes will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.With increasing amounts of complex, the infinite adsorption, the exhaustion and the rate constant of dyeing for nylon decrease.     

Fading phenomena of azo oil dye in anionic-nonionic surfactant solutions III. The effect of solubilizates on the fading behavior of azo oil dye in mixed surfactant systems

The effects of solubilizates on the fading behavior of 4-phenylazo-1-naphthol (4-OH) in aqueous solutions of anionic-nonionic mixed surfactant systems are described; the systems studied are sodium dodecyl sulfate (SDS) — octadecyl poly(oxyethylene) ethers (C₁₈POE₂₀). The fading rate of 4-OH in the mixed solution was independent of the addition of octane. By adding octanoic acid, the rate became faster. On the other hand, the 1-octanol slowed the rate. The fading speed of 4-OH decreased as the concentration of the alcohol and the number of carbon atoms in the alcohol molecule, used as a solubilizate, increased. The sizes of mixed micelles penetrated by the solubilizate were dependent on the kind of oily materials and on the alkyl chain lengths in the molecules of normal higher alcohols. Relative viscosities and effective specific volumes in the mixed micellar solutions increased with the increase in the concentration of 1-octanol and octanoic acid, and with increasing the number of alkyl groups in the alcohol molecule. The effect of solubilizates on the fading behavior of 4-OH was found to be dependent on the differences in their solubilization sites in mixed micelles. A solubilizate with a strong polar group supported a hydrophilic-hydrophilic interaction, whereas one including a weak polar group did not.     

Characterization of aqueous solution of cresol red as food irradiation dosimeter

Dilute aqueous solution of cresol red has been evaluated spectrophotometrically as possible gamma rays dosimeter. A 0.10 mM solution of cresol red was irradiated by gamma rays using a cobalt-60 radiation source. The absorbance spectra of the unirradiated and irradiated solutions were recorded using double beam scanning spectrophotometer. The absorbance of the solution before and after irradiation was measured at 434 nm (λ_max) as well as at other wavelengths (415, 448 and 470 nm). Various parameters, such as Absorbance (A), ΔA, %A, -log A and log A_o/A_i were plotted against radiation dose, in order to check the response of cresol red solution and its possible use as chemical dosimeter. The response plots of A, ΔA, and %A versus absorbed dose showed that the solution can be used as a radiation dosimeter in a dose range up to 0.82 kGy. Using response plots of -log A and log A_o/A_i, the useful dose range can be extended up to 1.65 kGy; which are useful dose ranges for food irradiation applications. Stability studies of cresol red solution at different light and temperature conditions for pre- and post-irradiated storage of the dosimetric solutions suggested that aqueous solution of cresol red is highly stable in dark, under fluorescence light and at room temperature up to 150 days     

Redox switchable NIR dye derived from ruthenium-dioxolene-porphyrin systems

Newly synthesised Ru(bp)2(sq)(+)-derivatives, covalently linked to a porphyrin-core, show very high epsilon values in the NIR region; which exhibit fast on/off switching depending on the redox state of the coordinated dioxolene functionality.