Development of green extractions of natural compounds is an ongoing challenge for researches. The aim of the study was to evaluate the extraction of bioactive compounds (BACs) from oregano combining ...an experimental procedure with a theoretical approach using two computational simulation methods, Hansen solubility parameters (HSP) and conductor-like screening model for real solvents (COSMO-RS) software. In this study, the high-voltage electrical discharge-plasma (HVED) was used as one of new promising green extraction techniques. Optimization of processing extraction parameters (argon and nitrogen for generation of plasma, voltage―15 kV, 20 kV, and/or 25 kV), frequency (100 Hz), pulse duration (400 ns), and treatment time (3 and 9 min) was done using software STATGRAPHICS. Oregano extracts were prepared by pharmacopoeia, 1 g per 50 mL of solvents (water or aqueous ethanol (25 and 50% v/v) treated by HVED. Extraction process was controlled by analytical methods (determination of total phenolic compounds (TPC); antioxidant properties by electronic paramagnetic resonance (EPR), 2,2-diphenyl-2-picrylhydrazyl (DPPH) free radical assay; near-infrared (NIR) spectroscopy; and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) characterization of phenolic compounds, and changes during and after extraction process were investigated. Process follows six principles of green extractions. Theoretical results were in line with experimental for solvent selection; ethanol had higher potential of solubility of BACs than water. Results showed that HVED, as a green extraction method, confirmed high potential for extraction of BACs from oregano with increased yield of individual BACs and TPC in obtained extracts and increased antioxidant activity, compared with untreated samples.
Electron spin resonance (ESR) dosimetry aims to investigate different materials for the purpose of reconstruction of the dose absorbed by the victims of radiological and nuclear accidents. The ...soda-lime glass is very popular as retrospective dosimeter due its availability. In the dose range below 2 Gy soda-lime glass ESR signal of radiation induced radicals overlaps with the background ESR signal and limit the dose reconstruction. Recently it was shown that the behavior of g-effective value is useful tool for dose reconstruction for triage application. Therefore, in this research, effects of temperature on the time stability of the g-effective values, the temperature dependence of the g-effective values and on the previously proposed g-effective approach were studied. The time stability was tested for the temperatures 200 K and 300 K. The g-effective values remained unchanged at both sample temperatures within 2 months after irradiation.
The temperature dependence of the g-effective values was investigated in the range from 180 K to 300 K for the samples irradiated with doses 0.3, 0.5, 0.7, 1, 2 and 5 Gy. The results show that temperature of the sample is not influencing the g-effective value. Furthermore, all of the samples exhibit previously proven approach for the g-effective value exponential dependence on the dose. The temperature dependence of the approach was investigated within temperature range from 200 K to 300 K and the results are consistent with previous research. This proves that g – effective value is stable parameter with temperature and within 2 months after irradiation and therefore useful for application in retrospective dosimetry.
•Time stability of g-effective was measured at two temperatures.•Temperature dependence of g-effective value was monitored for different doses.•Dose dependence on g-effective values was studied at different temperature.•No change in g-values with temperature and time was observed.
Poly(lactic acid) (PLA), compared to other biodegradable polymers, has one of the highest consumption volumes in the world. Due to its specific properties, especially those that make it ecologically ...acceptable, it has a wide application from food packaging to medical implants. In this work, commercially available 3D printing filament of PLA was used. The objective was to investigate the effects of γ-radiation on structural changes, mechanical and thermal behaviour of the material. The samples were irradiated with total doses of 25 kGy, 50 kGy, 100 kGy and 200 kGy. The experimental techniques used to investigate the structural changes in PLA filaments were electron spin resonance (ESR) and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and universal testing machine were applied in monitoring changes in thermal and mechanical behaviour, respectively. The formation and stability of free radicals were studied by ESR, which confirmed that the radical concentration depends on the applied absorbed dose, while the spectral lineshape appears to be dose independent. The loss of the ESR signal, directly related to the decrease of radical concentration, was monitored as a function of time for all applied absorbed doses. The breaking force and the Young's modulus were determined and compared. Results have shown that both the concentration and decay rate constant of radicals depend on the absorbed dose. Compressive strength test, a new approach in considering the mechanical changes in irradiated PLA indicated a loss of material elasticity and an increase of brittleness by increasing absorbed dose.
•PLA filaments irradiated in 60Co γ-source up to 200 kGy were studied.•Based on ESR results, the dose dependent radical decay rate constants were determined.•Mechanical changes were studied by a compressive strength test – a new approach.
Abstract
In this work, we report some preliminary results regarding the analysis of electron spin resonance (ESR) response of soda-lime samples used for retrospective dosimetry. Six different ...soda-lime glass batches were evaluated after irradiation. We compared several dose reconstruction techniques: saturation method, subtraction method and g-effective, geff, approach. The differences were observed and discussed. ESR signal responses of soda-lime glass samples to different radiation doses for the triage application were investigated. Results confirmed that geff approach has potential for the identification and dosimetry of irradiated soda-lime glass samples using either additive dose method or only calibration curve.
Calcium sulfate (CS) is a reasonable alternative to autogenous dental bone graft and is used as a bone filler or for the treatment of bone defects. Medical grade CS must be sterilized, usually by ...gamma-irradiation. In this study the structures of CS polymorphs, calcium sulfate dihydrate and calcium sulfate hemihydrate, have been investigated with electron paramagnetic resonance (EPR) spectroscopy, X-ray diffraction, thermogravimetric analyses and infrared spectroscopy. The influences of saline and artificial saliva on gamma-induced radical concentrations have been monitored.
•Study of γ-induced radicals in calcium sulfate hemihydrate and dihydrate.•Saline and saliva influence radical concentration in both polymorphs.•In calcium sulfate-based graft materials faster radical decrease with saliva.•Higher ratio of hemihydrate decreases radical concentration.
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•The influence of TiO2 nanoparticles and titanate nanotubes on calcium phosphates spontaneous precipitation was investigated for the first time.•Uncommon dual effect on the rate of ...amorphous to crystalline calcium phosphate transformation was observed.•No significant structural difference between calcium deficient hydroxyapatite formed on different nanomaterials was observed.
Calcium phosphates (CaPs) composites with different TiO2 nanomaterials (TiNMs) have recently attracted attention due to their potential application as implant materials for hard tissue regeneration. Among different synthetic routes for such composites, biomimetic synthesis attracts special attention as a green synthesis route. To rationalize biomimetic synthesis, the influence of surface structure and surface charge density of different TiNMs on CaPs precipitation should be determined. In this paper, for the first time, the influence of TiO2 nanoparticles (TiNPs) and titanate nanotubes (TiNTs) on CaPs spontaneous precipitation was investigated. In addition, the ability of TiNMs to induce CaPs formation in corrected simulated body fluid (c-SBF) was tested. The advancement of the CaPs precipitation was followed by potentiometric measurements, while the obtained materials were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS), powder X-ray diffraction (PXRD), scanning (SEM) and transmission (TEM) electron microscopy, electron paramagnetic resonance spectroscopy (EPR), Brunauer-Emmett-Teller surface area analysis (BET), dynamic (DLS) and electrophoretic light scattering (ELS), atomic force microscopy (AFM) and thermogravimetric (TGA) analysis. Both TiNMs showed poor ability to promote CaPs formation in c-SBF which can be attributed to their low absolute zeta-potential value. However, during spontaneous precipitation, they exhibited uncommon dual influence on precipitation kinetics, i.e. inhibition of initially formed amorphous calcium phosphate (ACP) transformation at lower and promotion at higher concentrations. After one hour of reaction time, in the presence of both TiNMs, calcium deficient hydroxyapatite was formed (CaDHA). Morphology of the CaDHA depended on the type and concentration of TiNMs. However, PXRD, EPR and TGA characterization confirmed that there is no significant difference between CaDHA formed in the presence of different TiNMs, which indicates that CaDHA composites with different TiNMs could be prepared at similar conditions. In addition, they can be prepared in a much shorter time compared to the usual procedure with SBF. Obtained results confirm the importance of surface structure and charge in CaPs – TiNMs interactions. They as well contribute to a deeper insight into precipitation processes on the nanosurfaces, which enables a rational approach not only in the biomimetic synthesis of novel biocomposites for hard tissue regeneration but also of composites for other applications.
Biological and physical retrospective dosimetry are recognised as key techniques to provide individual estimates of dose following unplanned exposures to ionising radiation. Whilst there has been a ...relatively large amount of recent development in the biological and physical procedures, development of statistical analysis techniques has failed to keep pace. The aim of this paper is to review the current state of the art in uncertainty analysis techniques across the 'EURADOS Working Group 10-Retrospective dosimetry' members, to give concrete examples of implementation of the techniques recommended in the international standards, and to further promote the use of Monte Carlo techniques to support characterisation of uncertainties. It is concluded that sufficient techniques are available and in use by most laboratories for acute, whole body exposures to highly penetrating radiation, but further work will be required to ensure that statistical analysis is always wholly sufficient for the more complex exposure scenarios.
Mandatory eye lens monitoring for exposed workers who are liable to receive an equivalent dose to the lens of the eye higher than 15 mSv in one year, required by the new European Basic Safety ...Standard 2013/59 and the recommendation given by the International Commission on Radiological Protection to lower the annual dose limit for the lens of the eye to 20 mSv, have put dosimetry services using Panasonic dosemeters in a difficult position. There are no commercially available eye lens dosemeter holders to fit Panasonic TLD pellets. Therefore, we designed and 3D printed inexpensive, splash proof, reusable and comfortable holders to fit a Panasonic nLi2nB4O7:Cu pellet. The eye lens dosemeter consists of an acrylonitrile butadiene styrene (ABS) plastic holder with a slot for a TLD pellet. The slot with the TLD pellet is covered by a heat-shrink tube and shortly heated with hot air to shrink wrap. Results of combined energy/angular response measurements, for all photon radiation qualities used, relative to N-100 at 0° as the reference energy, were within IEC 62387:2012 limits. Additionally, electron spin resonance spectroscopy was used to test the effect of irradiation to the degradation properties of the plastic ABS holder. The dosemeter is to be worn fixed to a headband, close to the eye, on the left side of the head or in the middle of the forehead.
•An inexpensive and comfortable eye lens dosimeter holder can be 3D printed.•The 3D-printed holder fits a Panasonic TL single dosimeter element.•Holders with Li2B4O7 TLD are suitable for Hp(3) measurements in IR and IC.•Properties of the ABS plastic are not affected by radiation in low range.
ESR readout improvement of gamma-irradiated soda-lime glasses is presented by considering the dose-dependent differences in temperature behaviour of the radiation-induced signal and background ...signal, and effective difference in g-values of those two signals. Our experimental results demonstrate that the dose-dependent temperature behaviour can improve the ESR signal response for 30-80% in the dose range below 20 Gy by detection at 200 K compared to the room temperature signal readout. The application of improvement can be expected in the low-level dose range where the radiation-induced signal is comparable with an inhomogeneous background signal.
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