Severe plastic deformation: Nanostructured materials, metal-based and polymer-based nanocomposites: A review

Significant deformation of the metal structure can be achieved without breaking or cracking the metal. There are several methods for deformation of metal plastics. The most important of these methods are angular channel pressing process, high-pressure torsion, multidirectional forging process, extrusion-cyclic compression process, cumulative climbing connection process, consecutive concreting and smoothing method, high-pressure pipe torsion. The nanocomposite is a multiphase material which the size of one of its phases is less than 100 nm in at least one dimension. Due to some unique properties, metal-based nanocomposites are widely used in engineering applications such as the automotive and aerospace industries. Polymer-based nanocomposites are two-phase systems with polymer-based and reinforcing phases (usually ceramic). These materials have a simpler synthesis process than metal-based nanocomposites and are used in a variety of applications such as the aerospace industry, gas pipelines, and sensors. Severe plastic deformation (SPD) is known to be the best method for producing bulk ultrafine grained and nanostructured materials with excellent properties. Different Severe plastic deformation methods were developed that are suitable for sheet and bulk solid materials. During the past decade, efforts have been made to create effective Severe plastic deformation processes suitable for producing cylindrical tubes. In this paper, we review Severe plastic deformation processes intended to nanostructured tubes, and their effects on material properties and severe plastic deformation is briefly introduced and its common methods for bulk materials, sheets, and pipes, as well as metal background nanocomposites, are concisely introduced and their microstructural and mechanical properties are discussed. The paper will focus on introduction of the tube Severe plastic deformation processes, and then comparison of them based on their advantages and disadvantages from the viewpoints of processing and properties.

Evaluating algorithms of decision tree, support vector machine and regression for anode side catalyst data in proton exchange membrane water electrolysis

Nowadays, due to the various type of problems stemmed from using chemical compounds and fossil fuels which have widely influence on whole environment including acid rain, polar ice melting and etc., number of researches have been leading on replacing the nonrenewable energy sources with renewable ones in order to produce clean fuels. Among these, hydrogen emerges as a quintessential clean fuel, garnering substantial attention for its potential to be synthesized from the electric power generated by renewable sources like nuclear and solar energies. This is achieved through the employment of a proton exchange membrane water electrolysis (PEMWE) system, widely recognized as one of the most proficient and economically viable technologies for effecting the separation of H2O into H+ and OH-. In this study, the important affecting parameters on the anode side of catalyst in PEMWE and analyzed them by machine-learning (ML) algorithms through developing a data science (DS) procedure were discussed. Various machine learning models were subjected to comparison, wherein the Decision Tree models, specifically those configured with maximum depths of 3 and 4, emerged as the optimal choices, attaining a perfect 100% accuracy across both Dataset 1 and Dataset 2. Moreover, notable enhancements in accuracy values were observed for the Support Vector Machine (SVM) model, registering increments from 0.79 to 0.82 for Dataset 1 and 2, respectively. In stark contrast, the remaining models experienced a decrement in their accuracy scores. This phenomenon underscores the pivotal role played by the data generation process in rendering the models more faithful to real-world scenarios.

Application of multi-extruded fuel injectors for mixing enhancement of hydrogen gas at scramjet engine: computational study

Scramjet engines are considered a highly promising technology for improving high-speed flight. In this study, we investigate the effects of using multi-extruded nozzles on fuel mixing and distribution inside the combustion chamber at supersonic flow. Additionally, we explore the impact of an inner air jet on fuel mixing in annular nozzles. To model fuel penetration in the combustor, we employ a computational technique. Our study compares the roles of three different extruded injectors on fuel diffusion and distribution at supersonic cross-flow. Our findings reveal that the use of an inner air jet increases fuel mixing in the annular jet, while the use of extruded nozzles improves fuel distribution by enhancing the vortices between injectors. These results demonstrate the potential benefits of incorporating multi-extruded nozzles and inner air jets in the design of scramjet engines.

Fuel mixing enhancement of transverse coaxial air and fuel jet by upstream shock wave on in scramjet engines: numerical study

In this study, computational fluid dynamics (CFD) is used to disclose the impacts of upstream shock waves on fuel mixing of cross coaxial air and fuel jet at a scramjet engine. This study has tried to investigate the impact of three different lobe injectors (2-lobe, 3-lobe, and 4-lobe nozzle) on the fuel penetrations along the scramjet combustor. The supersonic air stream is M = 4 while cross hydrogen and air jet are released in sonic velocity. This study uses CFD simulations to analyze the effects of upstream shock waves on fuel mixing in the transverse coaxial jet and assess their potential for improving combustion efficiency. The results demonstrate that the usage of upstream shock waves significantly increases shock interactions and augments the vortex region downstream of the jet. Our results show that the impacts of shock waves on the penetration of fuel jet released from the coaxial lobe nozzle are substantial.

Synthesis and characterization of ternary chitosan-TiO2-ZnO over graphene for photocatalytic degradation of tetracycline from pharmaceutical wastewater

Various nanocomposites of TiO₂-ZnO, TiO₂-ZnO/CS, and TiO₂-ZnO/CS-Gr with different molar ratios were synthesized by sol-gel and ultrasound-assisted methods and utilized under UV irradiation to enhance the photocatalytic degradation of tetracycline. Characterization of prepared materials were carried out by XRD, FT-IR, FE-SEM, EDX and BET techniques. The TiO₂-ZnO with the 1:1 molar ratio supported with 1:2 weight ratio CS-Gr (T1‒Z1/CS1‒Gr2 sample) appeared as the most effective material at the optimized operational conditions including the tetracycline concentration of 20 mg/L, pH = 4, catalyst dosage of 0.5 g/L, and 3 h of irradiation time. As expected, the graphene had a significant effect in improving degradation results. The detailed performances of the T1‒Z1/CS1‒Gr2 were compared with ternary nanocomposites from EDX and BET results as well as from the degradation viewpoint. This novel photocatalyst can be effective in actual pharmaceutical wastewater treatment considering the applied operational parameters.

Graphene oxide-chitosan hydrogel for adsorptive removal of diclofenac from aqueous solution: preparation, characterization, kinetic and thermodynamic modelling

This work aimed at developing a natural compound-based hydrogel adsorbent to remove diclofenac as a model pharmaceutical from water. First, graphene oxide-chitosan (GO-CTS) and amine graphene oxide-chitosan (AGO-CTS) hydrogel adsorbents were synthesized via a facile mechanical mixing method. The synthesized materials were characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, and thermogravimetric analysis (TGA) techniques. In the second stage, adsorption experiments were conducted to determine the best GO to CTS ratio and find the optimized adsorption parameters, including the initial drug concentration, adsorbent dosage, pH, and temperature. The results showed that the optimal GO to CTS mass ratio is 2 : 5 and thus the same ratio was selected as the AGO to CTS mass ratio to understand the effect of amine-functionalization on removal efficiency. The optimal adsorption parameters were determined to be pH of 5, C _i of 100 ppm and dosage of 1.5 g L^-1, where 90.42% and 97.06% removal was achieved for optimal GO-CTS and AGO-CTS hydrogel adsorbents, respectively. Langmuir and Freundlich isotherms models were employed to investigate the adsorption behavior of diclofenac onto the synthesized hydrogels. The results revealed that the adsorption tends to be of the monolayer type and homogeneous, as the results were in better accordance with the Langmuir model than the Freundlich model. The thermodynamics of adsorption demonstrated that the adsorption is exothermic, exhibiting higher removal efficiency at lower temperatures. Furthermore, Gibb's free energy change of adsorption (ΔG) suggested that the adsorption is spontaneous, being more spontaneous for AGO-CTS than GO-CTS hydrogels. Finally, the regeneration ability of the hydrogel adsorbents was studied in five consecutive cycles. The adsorbent maintained its efficiency at a relatively high level for three cycles but a considerable decrease was observed between the third and the fourth cycle, indicating that the hydrogels were recoverable for three cycles.

Rifampicin resistance in Mycobacterium tuberculosis in Iran: a two-centre study

Multidrug-resistant tuberculosis remains a challenge. In this study, we investigated the incidence of rifampicin (RIF) resistance in Mycobacterium tuberculosis in a large number of pulmonary specimens. A two-center study in Tehran, the capital of Iran, was performed with 6624 pulmonary samples of patients with tuberculosis (TB) who were subjected to detection of RIF-resistant TB by GeneXpert MTB/RIF assay between May 2014 and July 2018. Conventional drug susceptibility testing was performed to confirm the results. Xpert MTB/RIF identified a total of 96 positives for M. tuberculosis, of which 5 (5.3%) samples were found to be RIF-resistant TB. All RIF-resistant and sensitive isolates detected by GeneXpert were phenotypically confirmed by drug susceptibility testing. These results indicated that the Xpert MTB/RIF test can be used as a rapid diagnostic method and can potentially decrease the morbidity associated with diagnostic delay and mistreatment.

Developing the Ternary ZnO Doped MoS2 Nanostructures Grafted on CNT and Reduced Graphene Oxide (RGO) for Photocatalytic Degradation of Aniline

Transition metal sulfide semiconductors have achieved significant attention in the field of photocatalysis and degradation of pollutants. MoS2 with a two dimensional (2D) layered structure, a narrow bandgap and the ability of getting excited while being exposed to visible light, has demonstrated great potential in visible-light-driven photocatalysts. However, it possesses fast-paced recombination of charges. In this study, the coupled MoS2 nanosheets were synthesized with ZnO nanorods to develop the heterojunctions photocatalyst in order to obtain superior photoactivity. The charge transfer in this composite is not adequate to achieve desirable activity. Therefore, heterojunction was modified by reduced graphene oxide (RGO) nanosheets and carbon nanotubes (CNTs) to develop the RGO/ZnO/MoS2 and CNTs/ZnO/MoS2 ternary nanocomposites. The structure, morphology, composition, optical and photocatalytic properties of the as-fabricated samples were characterized through X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray (EDX), elemental mapping, Photoluminescence (PL), Ultraviolet-Visible spectroscopy (UV-VIS), and Brunauer-Emmett-Teller (BET) techniques. The photo-catalytic performance of all samples was evaluated through photodegradation of aniline in aqueous solution. The combination of RGO or CNTs into the ZnO/MoS2 greatly promoted the catalytic activity. However, the resulting RGO/ZnO/MoS2 ternary nanocomposites showed appreciably increased catalytic performance, faster than that of CNTs/ZnO/MoS2. Charge carrier transfer studies, the BET surface area analysis, and the optical studies confirmed this superiority. The role of operational variables namely, solution pH, catalyst dosage amount, and initial concentration of aniline was then investigated for obtaining maximum degradation. Complete degradation was observed, in the case of pH = 4, catalyst dosage of 0.7 g/L and aniline concentration of 80 ppm, and light intensity of 100 W. According to the results of trapping experiments, hydroxyl radical was found to be the main active species in the photocatalytic reaction. Meanwhile, a plausible mechanism was proposed for describing the degradation of aniline upon ternary composite. Moreover, the catalyst showed excellent reusability and stability after five consecutive cycles due to the synergistic effect between its components. Total-Organic-Carbon concentration (TOC) results suggested that complete mineralization of aniline occurred after 210 min of irradiation. Finally, a real petrochemical wastewater sample was evaluated for testing the catalytic ability of the as-fabricated composites in real case studies and it was observed that the process successfully quenched 100% and 93% of Chemical Oxygen Demand (COD) and TOC in the wastewater, respectively.

Synthesis, characterization and evaluations of TiO2 nanostructures prepared from different titania precursors for photocatalytic degradation of 4-chlorophenol in aqueous solution

BACKGROUND

The aim of present work, was to synthesize the titanium nanoparticles (TNPs) and titanium nanotubes (TNTs) through the hydrothermal method with different precursors including the Titanium(IV) isopropoxide (TTIP) and Titanium(IV) bis(ammonium lactato)dihydroxide (TALH).

METHODS

TiO₂ nanostructures from different titania precursors as heterogeneous photocatalysis via hydrothermal method were synthesized. The as-prepared photocatalysts were characterized by X-ray diffraction, UV-Vis diffuse reflectance spectra, surface area measurements, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The TiO₂ photocatalysts were tested on the degradation of 4-Chlorophenol (4-CP) aqueous solution under UVC irradiation in a fabricated photoreactor.

RESULTS

The effect of operating parameters including the; initial 4-CP concentration (50-150 mg/L), catalyst dosages (0-3 g/L) and solution pH (4-10) on the photocatalytic activity of the prepared catalysts were systematically investigated. The results show that amongst the TiO₂ nanostructures under best conditions (initial 4-CP concentration of 50 mg/L, catalyst dosage of 2 g/L, pH of 4.0, Time of 180 min) TNT-P2 exhibited much higher photocatalytic degradation efficiency (82%) as compared with TNT-P1 (77%), TNP-P2 (51%), and TNP-P1 (48%). Moreover, the mechanism and tentative pathways of 4-CP degradation were explored. Finally, the kinetic study was performed and the Langmuir-Hinshelwood kinetic model was aptly fitted with the experimental data.

CONCLUSION

The results of the photocatalytic activity measurement demonstrated that one-dimensional TNTs shows enhanced photocatalytic performance as compared to the TNPs, therefore, indicating the beneficial feature of TNTs as a photocatalyst for the degradation of pollutants. Besides, TiO₂ nanostructures prepared from TALH precursor (TNT-P2 82%, TNP-P2 51%) has higher photocatalytic degradation efficiency as compared with TTIP precursors (TNT-P1 77%, TNP-P1 48%).

Photocatalytic decontamination of phenol and petrochemical wastewater through ZnO/TiO2 decorated on reduced graphene oxide nanocomposite: influential operating factors, mechanism, and electrical energy consumption

ZnO/TiO₂ anchored on a reduced graphene oxide (rGO) ternary nanocomposite heterojunction was synthesized via the multi-step method including hydrothermal, solvothermal and sol–gel methods. XRD, Raman, FESEM, EDX, Dot Mapping EDS, BET, FTIR, UV-VIS, TGA, and EIS techniques were utilized for characterizing as-synthesized catalysts. The XRD and Raman data proved the formation of anatase phase TiO₂ and wurtzite phase ZnO in the prepared samples. Further, the UV-Vis spectrum confirmed that the band gap value of ZnO/TiO₂ diminished on introduction of graphene oxide. Photocatalytic performance of the fabricated catalysts was investigated by decontamination of phenol in aqueous solutions. The effect of different operational factors such as pH, catalyst dosage, phenol concentration, and light illumination was investigated to find the optimum decontamination conditions. According to the results, complete degradation of phenol was achieved at pH = 4, catalyst dosage of 0.6 g L⁻¹, light intensity of 150 W, and phenol initial concentration of 60 ppm at 160 min under visible light illumination. With the addition of graphene oxide to the composite, a significant increase was detected in the photocatalytic performance due to the higher available surface area and lower electron/hole recombination rate. In addition, the scavenging experiments revealed that the ·OH is responsible for the degradation of phenol during the reaction. The degradation mechanism, economic performance, mineralization, and recyclability were also investigated. Kinetic studies confirmed that photocatalytic degradation process followed the pseudo-first-order kinetic model. A case of real wastewater treatment was used to examine the performance of the catalyst for real case studies.

ZnO/TiO₂ anchored on a reduced graphene oxide (rGO) ternary nanocomposite heterojunction was synthesized via the multi-step method including hydrothermal, solvothermal and sol–gel methods.

Morphological investigations of nanostructured V2O5 over graphene used for the ODHP reaction: from synthesis to physiochemical evaluations

Several V₂O₅ nanostructures, including the rod or belt-like, tube-like, needle-like and flower-like, were synthesized via the reflux and hydrothermal processes utilizing different templates such as monoamine, diamine, aromatic and alcoholic amines

A new technique for the strengthening of aluminum tungsten inert gas weld metals: using carbon nanotube/aluminum composite as a filler metal

The effect of multi-walled carbon nanotube (MWCNT) on the mechanical properties of aluminum multipass weld metal prepared by the tungsten inert gas (TIG) welding process was investigated. High energy ball milling was used to disperse MWCNT in the aluminum powder. Carbon nanotube/aluminum composite filler metal was fabricated for the first time by hot extrusion of ball-milled powders. After welding, the tensile strength, microhardness and MWCNT distribution in the weld metal were investigated. The test results showed that the tensile strength and microhardness of weld metal was greatly increased when using the filler metal containing 1.5 wt.% MWCNT. Therefore, according to the results presented in this paper, it can be concluded that the filler metal containing MWCNT can serve as a super filler metal to improve the mechanical properties of TIG welds of Al and its alloys.

Effect of Alpha Radiolysis on UO2Dissolution under Reducing Conditions

Effects of water radiolysis on the dissolution rate of UO2were studied by irradiating UO2colloids with an alpha particle beam of a cyclotron. The solution was kept under reducing conditions by applying a current of -10 or -50 nA and an ultrahigh purity argon bubbling. The solution pH was fixed at 6 during experiment. The particle flux was 1.1×1011α.cm−2.s−1entering in solution with an energy of 5 – 6 MeV. Despite initial reducing conditions water radiolysis increased the dissolution rate of uranium dioxide due to reaction with oxidizing radiolytic species such as H2O2, O2, OH•, HO2•, ClO3−. The monitoring of the redox potential showed that the solutions became rapidly oxidizing. The dissolution rate values were between 0.01 and 26 mg·m−2·d−1depending on the ratio of the irradiated UO2mass to the solution volume. This dependency is caused by hydrogen peroxide consumption at the UO2surface. The rate of hydrogen peroxide consumption by reaction with colloids corresponds to an equivalent rate of UO2oxidation/dissolution between 2 and 60 mg.m−2.d−1indicating that only a small fraction of produced H2O2is consumed by the dissolution reaction.

Effect of alpha radiolysis on doped UO2 dissolution under reducing conditions

The aim of the present work is to quantify the influence of alpha radioactivity of 225Ac doped UO2 on the dissolution rate under reducing conditions at pH 6. The doped or undoped material was prepared by precipitation and the size of particles was about 3 nm. The total alpha activity of the doped material was about 2000 MBq g-1 UO2, about 4 times higher than that of 15 years old spent fuel. The solution was kept under reducing conditions during the experiment by permanent electrochemical reduction under inert atmosphere. The results showed that the dissolution rate of doped material was a function of alpha activity and thus a function of the dose.

Speciation of technetium(IV) chloride under gamma irradiation

Speciation of Tc in aqueous solution is a complex phenomenon because several parameters intervene simultaneously. We show under gamma radiations, it is completely modified. At pH 8.5 TcO2is oxidized to Tc(VII) with a yield of 1.38×10−7mol J−1. At pH 1.5, it was demonstrated that Tc is present as hydroxylated species TcnOy(4n-2y)+(L. Vichot, M. Fattahi, M. Musikas: Radiochim. Acta 91, 263 (2003)). Its oxidation leads also to Tc(VII) with an experimental yield of 1.45×10−7mol J−1. In more acidic solutions, results are consistent with hydrolysis and oxidation of Tc(IV) to Tc(V). As for colloidal solutions of Tc(IV) or TcO2, they give Tc(VII) whereas solutions of TcCl62-at pH 0.5 and 1.5 do not lead directly to Tc(VII). Reduced states of Tc are very sensitive to radiation. Hydrolysis as well as polymerisation of Tc are accelerated. Furthermore the radiolytic processes are pH dependent.

Electrochemical aspects of radiolytically enhanced UO2dissolution

Experiments were performed, irradiating UO2colloids of 3 nm diameter by a 5 MeV alpha beam of a cyclotron. Both the dissolution rate of these colloids and the production rate of hydrogen peroxide have been measured. The experimentally measured corrosion rate of these colloids is very similar to the corrosion rates measured for bulk UO2samples, indicating on the one hand that similar reaction mechanism prevail and on the other hand that the UO2colloids are well representative for bulk UO2. The results were compared with two current models for radiolytical dissolution of spent fuel. Additionally a new coupling between water radiolysis reactions and spent fuel dissolution has been established. The coupling is not anymore based on rate constants for direct reaction of oxidants with UO2, but on the electrochemical coupling of anodic dissolution reactions with cathodic reduction of molecular and radical radiolysis products. The model not only describes well the experimental data, it also allows to predict both the establishment of corrosion potentials and of fractional reaction orders with respect to oxidant concentrations. Model results can also be compared with experimental data (corrosion potential ...) using UO2as an electrode.

Aqueous solution of UCl6(2-) in O2 saturated acidic medium: an efficient system to scavenge all primary radicals in spurs produced by irradiation

Absorbance measurements find the yield of the oxidation of U(IV) to be (8.75 +/- 0.05) x 10(-7) mol J(-1) in the (60)Co gamma radiolysis of aqueous solutions containing 4.4 x 10(-3) mol L(-1) U(IV) in the presence of O(2) saturated 2 mol L(-1) Cl(-) at pH = 0. This high value of oxidation yield suggests that all primary radicals formed by water decomposition are scavenged in these solutions. Simulations using a nonhomogeneous stochastic kinetic track model agree with the experimental results and are used to explain the mechanism for scavenging radicals and oxidation of U(IV).

Expression of neuronal nitric oxide synthase during embryonic development of the rat optic vesicle

The expression of neuronal nitric oxide synthase during the development of rat optic vesicle from embryonic day E14 to E18 was analyzed by histochemical procedures. The samples were frozen and cut on a cryostat and then studied by using the light microscope. Expression of nNOS was first seen on E14 in cells of Cajal-Retzius located in the marginal zone of optic vesicle. NADPH-d persisted in this layer throughout the embryonic period and began to decrease on E20. At E16, the optic vesicle has four NADPH-d positive layers. At E18, NADPH-d reactivity observed at low magnification showed five clearly defined layers. In the late stages, the most notable feature was a decrease in histochemical reaction of the marginal zone and at these stages, the layer IV showed less staining than the rest of the cortical plate. The observations suggest that nitric oxide is synthesized during embryonic life processes and this is related to maturational processes.

Microbial reduction of 99Tc in organic matter-rich soils

For safety assessment purposes, it is necessary to study the mobility of long-lived radionuclides in the geosphere and the biosphere. Within this framework, we studied the behaviour of (99)Tc in biologically active organic matter-rich soils. To simulate the redox conditions in soils, we stimulated the growth of aerobic and facultative denitrifying and anaerobic sulphate-reducing bacteria (SRB). In the presence of either a pure culture of denitrifiers (Pseudomonas aeruginosa) or a consortium of soil denitrifiers, the solubility of TcO(4)(-) was not affected. The nonsorption of TcO(4)(-) onto bacteria was confirmed in biosorption experiments with washed cells of P. aeruginosa regardless of the pH. At the end of denitrification with indigenous denitrifiers in soil/water batch experiments, the redox potential (E(H)) dropped and this was accompanied by an increase of Fe concentration in solution as a result of reduction of less soluble Fe(III) to Fe(II) from the soil particles. It is suggested that this is due to the growth of a consortium of anaerobic bacteria (e.g., Fe-reducing bacteria). The drop in E(H) was accompanied by a strong decrease in Tc concentration as a result of Tc(VII) reduction to Tc(IV). Thermodynamic calculations suggested the precipitation of TcO(2). The stimulation of the growth of indigenous sulphate-reducing bacteria in soil/water systems led to even lower E(H) with final Tc concentration of 10(-8) M. Experiments with glass columns filled with soil reproduced the results obtained with batch cultures. Sequential chemical extraction of precipitated Tc in soils showed that this radionuclide is strongly immobilised within soil particles under anaerobic conditions. More than 90% of Tc is released together with organic matter (60-66%) and Fe-oxyhydroxides (23-31%). The present work shows that ubiquitous indigenous anaerobic bacteria in soils play a major role in Tc immobilisation. In addition, organic matter plays a key role in the stability of the reduced Tc.

Histochemical assessment of nitric oxide synthase activity in aortic endothelial cells of streptozotocin-induced diabetic rats

Impaired endothelium-dependent relaxation of blood vessels is a common feature in diabetes, but the exact underlying mechanisms have not yet been clarified. In present study, endothelium-dependent vasorelaxation of aortic rings were evaluated in vitro in streptozotocin (STZ)-induced diabetic and age-matched control rats. Moreover, nitric oxide synthase (NOS) activity of aortic endothelial cells was assessed in both diabetic and healthy rats using histochemical staining for nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity. The results showed a significant decrease of endothelium-dependent relaxation in response to acetylcholine (ACh) in diabetic rings, compared with controls, that was accompanied by a remarkable attenuation of NOS activity in diabetic sections of rat aorta stained for NADPH-diaphorase. Furthermore, a membrane disruption of some endothelial cells was also observed in all diabetic sections. It can be concluded that a decrease in NOS activity together with a disruption of endothelial cell membrane play a major role in endothelial dysfunction observed in diabetes.

Gamma radiation effects on potassium pertechnetate in carbonate media

Gamma radiation effects on the stability of the oxidation state of radioelements and diffusion within the framework of nuclear waste repositories are often neglected, although it may influence physicochemical processes and thus transfer to biosphere and geosphere. This knowledge is essential to model transport phenomena. This study reports on effects of gamma irradiation on technetium in carbonate media, which is representative of natural systems. Depending on media compositions, the gamma irradiation on pertechnetate leads to formation of Tc(IV) only in the absence of carbonate. CO3*- radicals are able to re-oxidise technetium intermediate oxidation states to the +7 state.