Deionized Water Electrochemical Machining Hybridized with Alumina Powder Polishing for Microcavity of M-333 Mold Steel

An electrochemical machining (ECM) process for microcavity fabrication with deionized water (DI-water) and an ECM polishing hybrid with alumina powder of 1.0 μm grains on a single micro-EDM machine are proposed. The process adopts tungsten carbide as tool electrode and M-333 tool steel as the mold material. It reveals that employing the 30 μm/min feed rate with 50 mA and 0.2 ms of pulse-width is suitable for DI-water electrochemical machining. The DI-water ECM process can achieve an excellent surface roughness at Ra 0.169 µm on a semispherical round cavity. Combining the ECM with hybrid polishing with the alumina powder can achieve a better profile for a much deeper cavity than pure electrolytic discharge machining. The hybrid ECM polishing can efficiently finish a micro square insert of 0.6 mm length at 64 μm depth. Such ECM milling can achieve an S-shaped microchannel of radius 1.0 mm and a slot of 1.0 × 0.5 mm2 with 110 μm depth, demonstrating its feasibility and the surface integrity with accurate profile and roughness of Ra 0.227 μm. This study provides a cost-effective scheme for micro mold fabrication with a conventional micro-EDM machine tool and an intuitive and convenient optional process. However, some micro-electrical discharges occurred due to the breakdown of insulation, which creates micro craters on the surface of the parts.

Solvent Effect in Glycyrrhizic Acid Spectra (Absorption and Fluorescence)

In this research paper, a method built on UV/VIS spectrofluorophotometer and spectrophotometer by finding the fluorescence of glycyrrhizic acid in licorice root. Glycyrrhizic acid is an imperative active component present in licorice (Glycyrrhiza uralensis Fisch). Solvent effect had been studied in different solvents like deionized water and methanol. The differences between them were explored by the glycyrrhizic acid absorption and emission spectra. Under work conditions, i.e. 100% methanol solvent, a liquid ratio concentration 10−2 to 10−5 g /mL and second solvent with same conditions 100% deionized water in the same concentrations ,was done. The effect of the solvent was significant by change the value for λmax. The result was validated for parameters confines for Ex (λ Excitation) in different solvents. The results of absorption spectra obey Beer-Lambert's law. Because of the same property of these solvents (protic), the absence of a significant difference in the absorption spectra are shown. From florescence spectra, the spectrum at concentration 10−4 is the best for both solvents..

Influence of Different Dielectrics on Process Performance for Electrical Discharge-Assisted Milling of Titanium Alloy

Electrical discharge-assisted milling (EDAM) is an effective method for machining titanium alloys according to previous research. In this study, the influence of three different dielectrics (kerosene, EDM oil, and deionized water) on the EDAM performance was studied. Experimental studies reveal the influence of different dielectrics by analyzing the discharged signal, surface morphology, and elemental composition of the electrode. The results show that kerosene and EDM oil have a higher discharge frequency than deionized water. After a long discharge time, carbides and debris were generated during the machining process, which affected the micro-hardness and the discharge stability of the machined material. In EDAM, EDM oil can produce the best surface quality, and the surface roughness value was 34.93%, 87.92%, and 121.68% higher than that of kerosene, deionized water, and conventional milling (CM), respectively.

Joint transmutation of stable Cs and Sr isotopes in microbiological systems and prospects for accelerated deactivation of liquid radioactive waste

It was found during the research that in the experimental and control bioreactors, which at the beginning of the experiments contained only cesium and strontium, by the end of the experiments, yttrium and barium were found. These isotopes are formed as a result of low-energy nuclear reactions involving protons. In addition, in experimental bioreactors with an optimal composition, a two to threefold increase in the concentration of yttrium was recorded in comparison with the control non-optimal experiments. Accumulation of strontium and cesium in biomass was registered, which is explained by the process of biosorption. It is known that biosorption is the first step towards nuclear transformation (biotransmutation). At the same time, one of the main conditions for the nuclear transformation of biomass elements is its maximum efficient growth. An unexpected fact discovered during the experiment is that yttrium and barium were also found in the control bioreactor, where no biomass was added before the experiment, but only deionized water, glucose, and the initial stable cesium and strontium salts. It is important to note that these elements were not detected in the analysis of the initial salts, substrates, and deionized water. Most likely, the presence of yttrium and barium is due to inoculation of the control fluid of the bioreactor (where no biomass pellets were added) with microorganisms from the experimental bioreactors during their periodic opening for taking current pH samples and adding glucose. Also, the work recorded a decrease in the content of cesium and strontium in the liquid by 20% and 55%, respectively, which goes beyond the statistical error.

Degradation Behaviors of Two Epoxy Coatings After Dry/Wet-Accelerated Fog Exposure of Different Solutions

Applying organic coating is an important and effective approach for the protection of metal from corrosion. Weathering degradation and under-film corrosion are the two major important factors that cause the failure of organic coatings. In this work, the degradation investigation of two epoxy coatings (clear and pigmented coatings) was carried out under the dry–wet circulation of three different water fog solutions (deionized water, 0.5 wt% NaCl, 0.05 wt% NaCl + 0.35 wt% (NH4)2SO4) in 35 days. The apparent performance (pull-off adhesion and surface potentials) and electrochemical features [electrochemical noise and electrochemical impedance spectroscopy (EIS)] of the coating samples were monitored after dry–wet fog exposure. In our three accelerating systems of the fog atmosphere, the time that the detectable defects appeared on the surface of coating samples was far ahead in the mixed salt solution than that in the deionized water or 0.5 wt% NaCl solution. For a defective or damaged coating surface, the derived results by using the standard deviation method (SDM) or Fourier power spectrum (FPS) were rather higher than those obtained from EIS as a whole, while for the same coating, the degradation trend with time derived from EIS, SDM, FPS, and scanning Kelvin probe was consistent with each other.

Effect of TrisEDTA and Chlorhexidine 0.12% on an In Vitro-Defined Biofilm Representing the Subgingival Plaque Biofilm of the Dog

This study was designed to investigate the effects of chlorhexidine 0.12%, TrisEDTA (tromethamine ethylenediamintetraacetic acid), and a combination of chlorhexidine 0.12% and TrisEDTA on an in vitro plaque biofilm model comprised of three bacterial species commonly found in canine subgingival plaque. Porphyromonas gulae, Actinomyces canis, and Neisseria canis were grown in a biofilm on polished hydroxyapatite coated titanium alloy pucks for 72 h prior to exposure to one of four test solutions: TrisEDTA, chlorhexidine 0.12%, a combination of TrisEDTA and chlorhexidine 0.12%, or sterile deionized water as a control. Following exposure to the test solution, a sample was collected of the biofilm either immediately or following 24 h of additional incubation in a broth medium. Lower numbers of CFU/mL of Porphyromonas gulae resulted when the biofilm was treated with a solution of chlorhexidine 0.12% and TrisEDTA compared to with chlorhexidine 0.12% alone, TrisEDTA alone, or the control and so this solution can be said to be synergistic against Porphyromonas gulae in this controlled in vitro model. Greater reductions in the numbers of CFU/mL of Actinomyces canis and Neisseria canis resulted from treatment with chlorhexidine 0.12% alone than if treated with the combination of TrisEDTA and chlorhexidine 0.12%. When treated biofilm samples were allowed 24 h of additional growth in fresh media, greater variance resulted and this variance highlights the complex dynamics involved in bacterial growth within a biofilm.

Bioaccumulation of 137Cs and 60Co in freshwater plants

Contamination of the aquatic environment by the heavy metals and radionuclides has become a serious concern in the world. In our study, gamma-spectrometry of freshwater plants Bacopa monnieri and Egeria densa growing in cultivation media spiked with 137CsCl and 60CoCl2 was used for quantitative determination of bioaccumulation kinetic and distribution Cs+ and Co2+ ions in plant tissues. We found, that bioaccumulation of Cs and Co by fully immersed B. monnieri in Hoagland media (HM) was dependent on ion concentration in medium. Approx. 5-times lower Cs uptake 2.9 nmol/g (d.w.) was obtained in plants cultivated in 20% HM than from deionized water. The maximal Co uptake was 4-times higher than cesium uptake at the same conditions. Both Cs and Co were localized mainly in roots. The highest immobilization from roots to shoots was found in the case of Co uptake from deionized water with concentration ratio [Co]leaves : [Co]stem : [Co]root = 1.00 : 5.33 : 56.8. Cesium uptake by submerged plant E. densa was also strongly dependent on nutrients concentration in medium. However, in the case of cobalt uptake this dependence was less pronounced. Nutrients concentration also had a significant influence on distribution of Cs between stems and leaves of E. densa. Cesium was localized in leaves, however with increasing of nutrients concentration in cultivation media Cs was localized for account of stem. On the other hand, cobalt was immobilized mainly in leaves in whole range of nutrients concentration. Obtained data can serve as a models for understanding of phytoaccumulation of radionuclides from open water ponds and water channels in the vicinity of nuclear power plants and monovalent and bivalent metals from industrial sources of contamination.

Fresh and pasteurized orange juice analysis by TXRF

Orange is considered the main product of the Brazilian citrus agro-industrial complex. However, in the end of 2016, the ANVISA pointed out orange as a risky product due to contamination using pesticides in its cultivation. Therefore, in this context, an analysis of the chemical elements present in fresh and pasteurized orange juices becomes extremely relevant. Thus, this work aims to quantify the elements that are present in fresh and pasteurized orange juices, using the TXRF technique. Samples of fresh orange juice of Pêra variety were acquired in a store in the city of Londrina-PR, were analysed; three samples of oranges were purchased at a store in Itápolis, São Paulo and five more samples of Pêra orange were obtained in the rural area. Samples of pesticides used in orange cultivation were quantified, and three different trademarks of pasteurized juice were analysed. In some of the samples that were collected in Itápolis-SP market, lead (Pb) element was quantified, however its concentration was within the limit established by Brazilian legislation. The aluminium (Al) element was detected in all samples of pasteurized orange juice, showing the influence of the packaging on the elemental concentration of the juice. All pesticides quantified in this work showed a significant concentration of some micro-contaminants, but when the pesticide was diluted in deionized water, those micro-contaminants could not be quantified.