Study of the effect of dose-rate on radiation-induced damage to human erythrocytes

Human erythrocytes suspended in an isotonic Na-phosphate buffer, pH 7.4 (hematocrit of 2%) were irradiated with γ-rays at three dose-rates of 66.7, 36.7, 25 Gy min⁻¹ in order to investigate the influence of the dose-rate on radiation-induced membrane damage, hemoglobin oxidation and loss of reduced glutathione.The obtained results showed that such processes as erythrocyte hemolysis, lipid and protein destruction depend on the radiation dose-rate. The parameter values describing these processes showed an inverse dose-rate effect.     

The influence of Se doping upon the phase change characteristics of GeSb2Te4

Se substituted GeSb₂Te₄ films have been investigated for property contrast using electrical four-point-probe measurements, in-situ X-ray diffraction (XRD), a static tester probing the optical changes and atomic force microscopy (AFM). The temperature dependent sheet resistance measurements show two transitions at 125 and 262 °C. The first transition at 125 °C is accompanied by a large resistance change of three orders of magnitude. The resistance change for the second step is less pronounced. In-situ X-ray scattering experiments evidence that the first steep change in resistance is due to an amorphous → NaCl type structural transformation. The second change is caused by the transition from the cubic structure to the stable rhombohedral phase. Power–time effect (PTE) diagrams recorded to monitor the optical contrast of the films upon laser irradiation exhibit a fast recrystallization time of about 100 ns. The change of film roughness and topography between the amorphous and crystalline phase has been determined by AFM.     

Radiation damage to human erythrocytes. Relative contribution of hydroxyl and chloride radicals in N2O-saturated buffers

The erythrocyte suspensions in Na-phosphate buffered isotonic NaCl solution (PBS) or Na-phosphate isotonic buffer (PB) (hematocrit 1%) were irradiated with the dose of 400 Gy under N₂O. Erythrocytes were incubated in the medium in which the cells were irradiated or in fresh PBS. The level of damage to cells was estimated on the basis of the course of post-radiation hemolysis and hemoglobin (Hb) oxidation. The medium in which the cells were irradiated and incubated influenced the course of the post-radiation hemolysis and Hb oxidation as well as some other parameters. We discussed the contribution of hydroxyl and chloride radicals in the initiation of erythrocyte damage and oxygen modification of these processes.     

New applications of the VDmax approach to substantiation of preselected sterilization doses

The VD_max approach for substantiation of 25 kGy has been in use for more than 10 years. VD_max methods are included in ISO 11137-2:2006 and AAMI TIR33:2005. ISO Technical Specification, 13004, is under development that will include sterilization doses from 15 to 35 kGy.For substantiation of a sterilization dose for very low bioburden products, less than or equal to 0.3, values of VD_max have now been derived and tabulated for a sterilization dose of 12.5 kGy.Products have been encountered that have both low bioburden and a relatively low maximum dose. In several situations, existing tabulated VD_max values could not be effectively used; in one such situation, the average bioburden was too high to substantiate a 15 kGy sterilization dose and the use of a 17.5 kGy sterilization dose was not practicable due to the likelihood of exceeding the product's maximum acceptable dose. For this product, values of VD_max were derived and tabulated for substantiation of a 16.1 kGy sterilization dose.Values of VD_max have been derived and tabulated for the substantiation of sterilization doses linked to a sterility assurance level (SAL) of 10^?3. To offer a potential alternative to aseptic processing, the notion of using an “aseptic processing equivalent dose”, 10^?4 SAL, has been investigated along with the use of alternate model populations for calculation of VD_max values.     

Improved electrochemical performance of SrCo0.8Fe0.2O3−δ–La0.45Ce0.55O2−δ composite cathodes for IT-SOFC

The performance of the SrCo_0.8Fe_0.2O_3−δ(SCF)–La_0.45Ce_0.55O_2−δ(LDC) composite cathodes was studied in this paper. The composite cathodes were prepared by screen-printing, and then sintered at 1200 °C for 2 h. Electrochemical impedance spectroscopy (EIS) and cathodic polarization test were carried out to investigate the electrochemical properties of the composite cathodes. The results showed that the composite cathodes had superior electrochemical performance compared to that of the pure SCF cathodes. Through optimizing the structures of composite cathodes, the cathodic overpotential of triple-layer SCF–LDC composite cathodes was only 23 mV at 0.3 A cm⁻². The specific ohmic resistance, charge transfer resistance and gas phase diffusion resistance of the triple-layer SCF–LDC cathodes were the lowest for the SCF–LDC composite cathodes, and they were 0.1 Ω cm², 0.01 Ω cm² and 0.1 Ω cm² respectively at 800 °C. The changes were attributable to the enlargement of triple phases boundary (tpb) and enhancement of the adhesion between electrode and electrolyte by adding LDC to the cathode material.     

The effect of 60Co (γ-ray) irradiation on the electrical characteristics of Au/SnO2/n-Si (MIS) structures

The effect of ⁶⁰Co (γ-ray) irradiation on the electrical properties of Au/SnO₂/n-Si (MIS) structures has been investigated using the capacitance–voltage (C–V) and conductance–voltage (G/ω−V) measurements in the frequency range 1 kHz to 1 MHz at room temperature. The MIS structures were exposed to γ-rays at a dose rate of 2.12 kGy/h in water and the range of total dose was 0–500 kGy. It was found that the C–V and G/ω−V curves were strongly influenced with both frequency and the presence of the dominant radiation-induced defects, and the series resistance was increased with increasing dose. Also, the radiation-induced threshold voltage shift (ΔV_T) strongly depended on radiation dose and frequency, and the density of interface states N_ss by Hill–Coleman method decreases with increasing radiation dose.     

Exhaustive radiolysis of 11 mM aqueous benzene solutions: effect of added oxygen

The gamma radiolysis of aqueous benzene solutions was studied under various conditions (oxygenated, aerated and anoxic) to ascertain the role that oxygen plays in the destruction of benzene. For the oxygenated and aerated systems, phenol and biphenyl were the major quantified products. For the anoxic system, phenol was the sole quantified product. Benzene was initially consumed with approximately the same yield in each of the three systems; G(–benzene) was 0.49 μmol J^–1. Initial yields of phenol, G(phenol), were found to be 0.12, 0.060 and 0.030 μmol J^–1 for the oxygenated, aerated and anoxic systems, respectively. Biphenyl was initially formed with G=0.028 and 0.019 μmol J^–1 in the oxygenated and aerated systems, respectively. The percent conversion of benzene to CO₂ after an absorbed dose of 2500 kGy was 55.1%, 30.5% and 12.5%, respectively, for the oxygenated, aerated and anoxic systems. The last traces of benzene disappeared by a dose of ca. 60 kGy in all three systems. A mechanism was proposed for each system that depended upon the presence or absence of O₂. The total solution toxicity for each system was calculated by summing the individual toxicities of benzene and each quantified product. For the oxygenated and aerated systems, the total solution toxicity was found to go through a maximum at a dose of 22 kGy and then decrease to a value below that of the original solution. The total solution toxicity of the anoxic system was found to decrease from the onset of irradiation.     

High-performance bilayered electrolyte intermediate temperature solid oxide fuel cells

The ESB/GDC bilayer electrolyte concept has been proved to improve open circuit voltage and reduce the effective area specific resistance of SOFCs utilizing a conventional single-layer GDC electrolyte. However, high performance from such bilayer cells had not yet been demonstrated. The main obstacles toward this end have been fabrication of anode-supported thin-film electrolytes and the reactivity of ESB with conventional cathodes. Recently, an ESB-compatible low area specific resistance cathode was developed: microstructurally optimized Bi₂Ru₂O₇-ESB composites. In addition, we recently developed a novel anode functional layer which can significantly enhance the performance of SOFC utilizing GDC electrolytes. This study combines these recent achievements in SOFC studies and shows that exceptionally high performance of SOFC is possible using ESB/GDC bilayer electrolytes and Bi₂Ru₂O₇-ESB composite cathodes. The result confirms that the bilayer electrolyte and the Bi₂Ru₂O₇-ESB cathode can increase the open circuit potential and reduce the total area specific resistance. The maximum power density of the bilayered SOFC was improved to 1.95 W cm^?2 with 0.079 Ω cm² total cell area specific resistance at 650 °C. This is the highest power yet achieved in the IT range and we believe redefines the expectation level for maximum power under IT-SOFC operating conditions.     

Gamma ray induced changes on vibrational spectroscopic properties of strontium alumino-borosilicate glasses

The present investigation reports the effect of influence of aluminum ions on radiation damage of strontium borosilicate glasses studied by means of spectroscopic (viz., optical absorption (OA), infrared and Raman spectra). The composition of the glasses chosen for the study is 40SrO–xAl₂O₃–(15-x) B₂O₃–40SiO₂ (x = 5, 7.5, 10), all in mol%. The glasses were synthesized by conventional melt quenching method. Later, the samples were exposed to gamma (γ) radiation dose of strengths 10 kGy and 30 kGy with a dose rate of 1.5 Gy/s using ⁶⁰Co as radiation source. The infrared spectra (IR), Raman spectra and optical absorption (OA) spectra of the samples were recorded at ambient temperature before and after irradiation. The OA spectra of the pre-irradiated samples do not exhibit any absorption bands in the UV–vis regions and IR and Raman spectra exhibited conventional vibrational bands due to different borate, silicate AlO₄ and AlO₆ structural units. The OA spectra of post irradiated samples exhibited a broad absorption band in the wavelength region 600–750 nm; it is attributed to electron trapped color centers. The intensity of this peak is observed to increase with increase of the γ-ray dose. Considerable changes in the intensities of various bands in the IR and Raman spectra were also observed. The changes were explained based on structural modifications taking place in the glass network due to γ-ray irradiation and finally it is concluded that the glasses mixed with 10.0 mol% of Al₂O₃ are relatively more radiation resistant.     

In situ growth of polymer electrolytes on lithium ion electrode surfaces

Polyacrylonitrile (PAN) films were grown on glassy carbon, nickel foam and MnO₂ substrates by cathodic electropolymerisation of acrylonitrile in acetonitrile with tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte. The electronic barrier properties of the films were confirmed by impedance spectroscopy of carbon |PAN| Hg cells while the ionic resistance of the films varied from 200 kΩ cm² in the dry state to 1.4 Ω cm² when plasticised with 1 M LiPF₆ in propylene carbonate. A galvanic cell was prepared by successive electrodepositions of MnO₂ and PAN on a carbon substrate, using liquid lithium amalgam as the top contact. The cell showed a stable open circuit potential and behaved normally under the galvanostatic intermittent titration technique (GITT).     

Surface properties and photoactivity of TiO2 treated with electron beam

The improvement of the TiO₂-photoactivitiy by electron beam treatment (1 MeV) as a function of the absorbed radiation dose (MGy) is reported. The radiation-induced effects in the TiO₂ crystal structure, e.g. change of the Ti³⁺/Ti⁴⁺ ratio, increase of the photoactivity, etc. were investigated. Three methods were implemented in this respect: for the change of the TiO₂ crystal structure X-ray photoelectron spectroscopy and photoluminescence spectroscopy were applied. The photocatalytic activity of the EB-treated TiO₂ was tested by taking the degree of methylene blue photodegradation as a measure of the achieved effect. The obtained experimental data of all testing methods showed that in TiO₂ at an absorbed dose of 0.5 MGy optimum changes in crystal structure of the catalyst occur, resulting in the highest photocatalytic efficiencies.     

Effect of electron beam radiation dose on the foam formation in pre-ceramic polymer

Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N₂ atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm^?3.     

Catalytic conversion of CO2–CH4 mixture into synthetic gas—Effect of electron-beam radiation

The radiolysis of methane (0.7 MeV electron beam) was studied as a function of its concentration at two doses: 5 and 20 kGy. In both cases the G (–CH₄) value raised with the increase of the substrate concentration. Thereby the yields observed at 20 kGy are much lower, because of recombination processes. Results are also reported on the conversion of the gas mixture CH₄:CO₂:He=1:1:1 into synthetic gas (H₂/CO) at 500 °C, using two catalysts : (N5) and (N20), containing 5 wt% Ni and 20 wt% Ni, respectively, supported on γ-Al₂O₃. In an experimental series the catalysts (N5) and (N20) were treated by irradiation (4 MGy dose) before use. The highest conversion yields (above 35%) were observed by implementation of N5 and N20 catalyst at 500 °C under the influence of electron beam radiation.     

Advanced oxidation of aromatic VOCs using a pilot system with electron beam–catalyst coupling

The decomposition of volatile organic compounds (VOCs) using a pilot system of electron beam (EB)–catalyst coupling was investigated. Two aromatic VOCs, toluene (1800 ppmC) and o-xylene (1500 ppmC), were irradiated with a dose range of 0–10 kGy at room temperature. The removal efficiencies for toluene and o-xylene were 92.4% and 94.5%, respectively, under a 10 kGy absorbed dose condition, which were higher than the results of 45.7% and 52.3% when EB-only was used, respectively. The CO₂ selectivity approached 100% for both toluene and o-xylene using the EB-catalyst coupling system, while the concentrations of O₃ formed were 0.02 ppm (toluene) and 0.003 ppm (o-xylene) at 10 kGy. The aerosol concentration was also measured as 43.2 μg/m³ (toluene) and 53.4 μg/m³ (o-xylene) at 10 kGy absorbed dose.     

Effects of electron beam irradiation on the photoelectrochemical properties of TiO2 film for DSSCs

TiO₂ has been widely utilized for various industrial applications such as photochemical cells, photocatalysts, and electrochromic devices. The crystallinity and morphology of TiO₂ films play a significant role in determining the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, the preparation of nanostructured TiO₂ films by electron beam irradiation and their characterization were investigated for the application of DSSCs. TiO₂ films were exposed to 20–100 kGy of electron beam irradiation using 1.14 MeV energy acceleration with a 7.46 mA beam current and 10 kGy/pass dose rates. These samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) analysis. After irradiation, each TiO₂ film was tested as a DSSC. At low doses of electron beam irradiation (20 kGy), the energy conversion efficiency of the film was approximately 4.0% under illumination of simulated sunlight with AM 1.5 G (100 mW/cm²). We found that electron beam irradiation resulted in surface modification of the TiO₂ films, which could explain the observed increase in the conversion efficiency in irradiated versus non-irradiated films.     

Enhanced performance of an anode-supported YSZ thin electrolyte fuel cell with a laser-deposited Sm0.2Ce0.8O1.9 interlayer

A power density of over 1.4 W cm^?2 at 0.7 V was achieved at 750 °C for an anode-supported YSZ thin electrolyte fuel cell with a dense Sm_0.2Ce_0.8O_1.9 (SDC) interlayer fabricated by pulsed laser deposition, while the cell with a conventional porous SDC interlayer exhibited only 0.8 W cm^?2 at this voltage. The dense SDC interlayer significantly reduced the ohmic resistance of the fuel cell. For example, at 750 °C, the ohmic resistance of the fuel cell with a dense SDC interlayer was 0.08 Ω cm²; while that of the cell with a porous SDC interlayer fabricated by conventional screen-printing was 0.16 Ω cm². The pronounced reduction in ohmic resistance might be due to the fully dense structure and thus improved electrical conductivity of the SDC interlayer, increased contact area at the interface between the dense SDC interlayer and the YSZ electrolyte, and suppressed Zr migration into the SDC interlayer.     

High-surface-area microporous carbon as the efficient photocathode of dye-sensitized solar cells

This paper reports on the application of cornstalks-derived high-surface-area microporous carbon (MC) as the efficient photocathode of dye-sensitized solar cells (DSCs). The photocathode, which contains MC active material, Vulcan XC–72 carbon black conductive agent, and TiO₂ binder, was obtained by a doctor blade method. Electronic impedance spectroscopy (EIS) of the MC film uniformly coated on fluorine doped SnO₂ (FTO) glass displayed a low charge-transfer resistance of 1.32 Ω cm². Cyclic voltammetry (CV) analysis of the as-prepared MC film exhibited excellent catalytic activity for I₃^?/I^? redox reactions. The DSCs assembled with the MC film photocathode presented a short-circuit photocurrent density (J_sc) of 14.8 mA cm^?2, an open-circuit photovoltage (V_oc) of 798 mV, and a fill factor (FF) of 62.3%, corresponding to an overall conversion efficiency of 7.36% under AM 1.5 irradiation (100 mW cm^?2), which is comparable to that of DSCs with Pt photocathode obtained by conventional thermal decomposition.     

A high performance nano-structure conductive coating on a Crofer22APU alloy fabricated by a novel spinel powder reduction coating technique

A nano-structure conductive coating was fabricated on a Crofer22APU alloy interconnect by an original coating strategy using Mn_0.9Y_0.1Co₂O₄ (MYC) novel spinel nanocrystalline powder. A unique treatment method by which the spinel powder was reduced was used to prepare the green coating. The resulting coating was about 12 μm in thickness, and was composed of MYC nanocrystalline with an average particle size of about 100 nm. The coating was well adhered with the substrate alloy. Less than 4 mΩ cm² of the area specific resistance (ASR) was obtained, and no obvious degradation was observed for a coated alloy (whose coating thickness was about 30 μm) after operated at 800 °C for 538 h under seven thermal cyclings. The coated alloy exhibited excellently electrical performance and long-term stability compared with the uncoated one. The exploration of the novel spinel powder reduction coating technique for alloy interconnect to obtain cheap coatings with excellent microstructure and performance showed a promising prospect for the practical application of solid oxide fuel cells (SOFCs).     

Effects of CuO addition to anode on the electrochemical performances of cathode-supported solid oxide fuel cells

A cathode-supported electrolyte film was fabricated by tape casting and co-sintering techniques. (La_0.8Sr_0.2)_0.95MnO₃ (LSM95), LSM95/Zr_0.89Sc_0.1Ce_0.01O_2?x (SSZ), and SSZ were used as materials of cathode substrate, cathode active layer, and electrolyte, respectively. CuO–NiO–SSZ composite anode was deposited on SSZ surface by screen-printing and sintered at 1250 °C for 2 h. The effects of CuO addition to NiO–SSZ anode on the performance of cathode-supported SOFCs were investigated. CuO can effectively improve the sintering activity of NiO–SSZ. The assembled cells were electrochemically characterized with humidified H₂ as fuel and O₂ as oxidant. With 4 wt.% CuO addition, the ohmic resistance decreased from 3 to 0.46 Ω cm², and at the same time the polarization resistance decreased from 3.4 to 0.74 Ω cm². In comparison with the cell without CuO, the maximum power density at 850 °C increased from 0.054 to 0.446 W cm^?2 with 4 wt.% CuO addition.     

The Potential of Dewa Leaves (Gynura Pseudochina (L) D.C) and Temu Ireng Rhizomes (Curcuma aeruginosa Roxb.) as Medicinal Herbs for Dengue Fever Treatment

There are a lot of natural resources that potentially used as herbal medicines in Indonesia. Some of the herbs, like Dewa leaves (Gynura pseudochina (L) D.C) and temu ireng rhizome (Curcuma aeruginosa Roxb.), were ussually used to increase number of thrombocytes in dengue patient. This current study was to determine the potential of dewa leaves (Gynura pseudochina (L) D.C) and temu ireng rhizome (Curcuma aeruginosa Roxb.) against the number of trombocytes, erythrocytes, and hematocrits level on male white rats (Rattus novergicus) by using Heparin Induction. Dosages of the extracts were 250 mg/kg BW and 500 mg/kg BW used for both dewa leaves and temu ireng rhizome. Extracts were given orally to the tested animals for seven continuous days. The number of trombocytes, erythrocytes, and hematocrites level were examine at day 7 using sysmex XE-5000 hematology analyzer. The result showed that the rat groups which were treated with dewa leaves extract at 500 mg/kgBW; temu ireng Rhizomes extract at 250 mg/kgBW and 500 mg/kgBW dosages had significant differences (α = 0.05) on number of thrombocytes. The percentages of thrombocytes number enhancement for temu ireng rhizomes extract 500 mg/kgBW, temu ireng rhizomes extract 250 mg/kgBW, dewa leaves extract 500 mg/kgBW were 26.98%, 24.48%, 19.44% respectively. The rats group which were treated with temu ireng Rhizomes extract at 500 mg/kgBW, dewa leaves extract at 250 mg/kgBW and 500 mg/kgBW had significant differences (α = 0.05) on erythrocytes number and hematocrits level enhancement. The percentages of erythrocytes number enhancement for dewa leaves extract at dose of 500 mg/kgBW and 250 mg/kgBW, temu ireng rhizomes extract 500 mg/kgBW were 9.59%, 9.11%, 9.02% respectively. The highest percentages of hematocrits level enhancement was given by dewa leaves extract at dose of 500 mg/kgBW (10,97%), suggesting that the extracts treatment would not trigger plasma leakage. Thus, dewa leaves extract at 500 mg/kgBW; temu ireng rhizomes extract at 250 mg/kgBW and 500 mg/kgBW dosages are potential as candidates to be medicinal herbs to increase numbers of thrombocytes on dengue fever treatment