Search results for: minimum inhibitory concentration (MIC)

Authors: K.Narasimhulu, Y. Pydi Setty

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The objective of this present study is the optimization of process parameters in biosorption of Ni(II) and Cd(II) ions by Pseudomonas putida using Response Surface Methodology in a Packed bed bioreactor. The experimental data were also tested with theoretical models to find the best fit model. The present paper elucidates RSM as an efficient approach for predictive model building and optimization of Ni(II) and Cd(II) ions using Pseudomonas putida. In packed bed biosorption studies, comparison of the breakthrough curves of Ni(II) and Cd(II) for Agar immobilized and PAA immobilized Pseudomonas putida at optimum conditions of flow rate of 300 mL/h, initial metal ion concentration of 100 mg/L and bed height of 20 cm with weight of biosorbent of 12 g, it was found that the Agar immobilized Pseudomonas putida showed maximum percent biosorption and bed saturation occurred at 20 minutes. Optimization results of Ni(II) and Cd(II) by Pseudomonas putida from the Design Expert software were obtained as bed height of 19.93 cm, initial metal ion concentration of 103.85 mg/L, and flow rate of 310.57 mL/h. The percent biosorption of Ni(II) and Cd(II) is 87.2% and 88.2% respectively. The predicted optimized parameters are in agreement with the experimental results.

Keywords: packed bed bioreactor, response surface mthodology, pseudomonas putida, biosorption, waste water

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Authors: Tesfaye Walle Mekonnen

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Maize is one of the most important staple food crops for most low-income households in the Sub-Saharan (SSA). Combined heat and drought stress is the major production threats that reduce the yield potential of biofortified maize and restrain various macro and micronutrient deficiencies highly prevalent in low-income people who rely solely on maize-based diets, SSA. This problem can be alleviated by crossing the biofortified inbred lines with different nutritional attributes, Fe, Zn, Protein, and Provitamin A, and developing agronomically superior and stable multi-nutrient maize of various genetic backgrounds. This aimed to understand the correlation between biofortified inbred lines per se and hybrid performance under combined heat and drought stress conditions (CSC). The experiment was conducted at CIMMYT, Zimbabwe, using α-lattice design with three replications. The hybrid effect was highly significant for zein fractions (α-, β-, γ- and δ-zein) zinc, (Zn), and iron (Fe) provitamin A, phytic acid, and grain yield. Under CSC, Fe, Zn concentration, provitamin A in grain and grain yield of hybrids were significantly decreased, however, the zein fraction content and phytic acid content increases in grain were increased under CSC. The phenotypic correlation between grain yield with Zn, Fe concentration, and Provitamin A in grain was strongly positive and higher under CSC than in well-watered conditions. The present investigation confirmed that under CSC, Fe, and Zn-enhanced hybrids could be forecasted to a certain scope based on the performance of and scientifically selected for desirable grain yield and related traits with CSC tolerance during hybrid development programs. In conclusion, the development of high-yielding and micronutrient-dense maize variety is possible under CSC, which could reduce the highly prevalent micronutrient in SSA.

Keywords: drought, Fe, heat, maize, protein, zein fractions, Zn

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Authors: Mehdi Seifollahi, Ashkan Forootan, Sajjad Bahrami Reyhan

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Due to the complexity of olefinic plants, various environmental pollutants exist such as NO_x, CO₂, Tar Water, and most importantly Spent Caustic. In this paper, instead of investigating ways of treating this pollutant, we evaluated the production in relation to plant’s variable items. We primarily discussed the factors affecting the quality of the output spent caustic such as impurities in the feed of olefin plant, the amount of injected dimethyl disulfide (DMDS) in furnaces, variation in feed composition, differences among gas temperatures and the concentration of caustic solution at the bottom of the tower. The results of the laboratory proved that in the formation of Red Oil, 1,3butadiene and acetaldehyde followed free radical and aldol condensation mechanism respectively. By increasing the injection rate of DMDS, Mercaptide amount increases in the effluent. In addition, pyrolysis gasoline accumulation is directly related to caustic concentration in the tower. Increasing naphtenes in the liquid feed augments the amount of 1,3butadiene, as one of the sources of Red Oil formation. By increasing the oxygenated compound in the feed, the rate of acetaldehyde formation, as the main source of Red Oil formation, increases.

Keywords: olefin, spent caustic, red oil, caustic wash tower

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Authors: Frederick Otite Ighovojah

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Corrosion in the oil and gas industries is one of the most common causes of failure. Such failure includes leaks in above-ground storage tanks (AGST). The involvement of microorganisms in the corrosion process in AGST systems is often ignored, and this outlines the need to investigate the effect of microbial corrosion in oil and gas facilities. This study's methodology comprised gathering generated water samples from a nearby AGST oil facility that was operating, which were then equally divided into two batch reactors, 1 and 2. Each batch reactor was filled with five prepared X60 coupons using sterilized forceps. To provide nutrients for the microorganisms in batch reactor 1 during the test period, 2g of NPK 15- 15-15 fertilizer was added on a weekly basis. To kill the microorganisms and significantly lower their concentration in the generated water, 5ml of dissolved ozone (a biocide) with a 0.5ppm concentration was added to batch reactor 2. The weight loss measurement (WLM) was used to evaluate for corrosion. Coupons were removed from each batch reactor, and weight loss was measured at every interval of 336 hrs for 2016 hrs. The overall results obtained indicated that coupons from the batch 1 reactor showed a higher corrosion rate and higher mass loss, and this was due to the metabolic production of an aggressive compound in the medium.

Keywords: AGST, microbial corrosion, reactor, X60 steel

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Authors: Müzeyyen Balçikanli, Erdoğan Özbay, Hakan Tacettin Türker, Okan Karahan, Cengiz Duran Atiş

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In this research, effect of curing time (TC), curing temperature (CT), sodium concentration (SC) and silicate modules (SM) on the compressive strength, chloride ion permeability, and water absorption capacity of alkali activated slag (AAS) concretes were investigated. For maximization of compressive strength while for minimization of chloride ion permeability and water absorption capacity of AAS concretes, best possible combination of CT, CTime, SC and SM were determined. An experimental program was conducted by using the central composite design method. Alkali solution-slag ratio was kept constant at 0.53 in all mixture. The effects of the independent parameters were characterized and analyzed by using statistically significant quadratic regression models on the measured properties (dependent parameters). The proposed regression models are valid for AAS concretes with the SC from 0.1% to 7.5%, SM from 0.4 to 3.2, CT from 20 °C to 94 °C and TC from 1.2 hours to 25 hours. The results of test and analysis indicate that the most effective parameter for the compressive strength, chloride ion permeability and water absorption capacity is the sodium concentration.

Keywords: alkali activation, slag, rapid chloride permeability, water absorption capacity

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Authors: Lai Peng, Cristina Pintucci, Dries Seuntjens, José Carvajal-Arroyo, Siegfried Vlaeminck

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Economic incentives drive the implementation of short-cut nitrogen removal processes such as nitritation/denitritation (Nit/DNit) to manage nitrogen in waste streams devoid of biodegradable organic carbon. However, as any biological nitrogen removal process, the potent greenhouse gas nitrous oxide (N2O) could be emitted from Nit/DNit. Challenges remain in understanding the fundamental mechanisms and development of engineered mitigation strategies for N2O production. To provide answers, this work focuses on manure as a model, the biggest wasted nitrogen mass flow through our economies. A sequencing batch reactor (SBR; 4.5 L) was used treating the centrate (centrifuge supernatant; 2.0 ± 0.11 g N/L of ammonium) from an anaerobic digester processing mainly pig manure, supplemented with a co-substrate. Glycerin was used as external carbon source, a by-product of vegetable oil. Out-selection of nitrite oxidizing bacteria (NOB) was targeted using a combination of low dissolved oxygen (DO) levels (down to 0.5 mg O2/L), high temperature (35ºC) and relatively high free ammonia (FA) (initially 10 mg NH3-N/L). After reaching steady state, the process was able to remove 100% of ammonium with minimum nitrite and nitrate in the effluent, at a reasonably high nitrogen loading rate (0.4 g N/L/d). Substantial N2O emissions (over 15% of the nitrogen loading) were observed at the baseline operational condition, which were even increased under nitrite accumulation and a low organic carbon to nitrogen ratio. Yet, higher DO (~2.2 mg O2/L) lowered aerobic N2O emissions and weakened the dependency of N2O on nitrite concentration, suggesting a shift of N2O production pathway at elevated DO levels. Limiting the greenhouse gas emissions (environmental protection) from such a system could be substantially minimized by increasing the external carbon dosage (a cost factor), but also through the implementation of an intermittent aeration and feeding strategy. Promising steps forward have been presented in this abstract, yet at the conference the insights of ongoing experiments will also be shared.

Keywords: mitigation, nitrous oxide, nitritation/denitritation, pig manure

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Authors: In-Hwan Baek

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Valsartan is a potent and highly selective antagonist of the angiotensin II type 1 receptor, and is widely used for the treatment of hypertension. The aim of this study was to investigate the pharmacokinetic properties of the valsartan in dogs following oral administration of a single dose using quantitative modeling approaches. Forty beagle dogs were randomly divided into two group. Group A (n=20) was administered a single oral dose of valsartan 80 mg (Diovan® 80 mg), and group B (n=20) was administered a single oral dose of valsartan 160 mg (Diovan® 160 mg) in the morning after an overnight fast. Blood samples were collected into heparinized tubes before and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12 and 24 h following oral administration. The plasma concentrations of the valsartan were determined using LC-MS/MS. Non-compartmental pharmacokinetic analyses were performed using WinNonlin Standard Edition software, and modeling approaches were performed using maximum-likelihood estimation via the expectation maximization (MLEM) algorithm with sampling using ADAPT 5 software. After a single dose of valsartan 80 mg, the mean value of maximum concentration (Cmax) was 2.68 ± 1.17 μg/mL at 1.83 ± 1.27 h. The area under the plasma concentration-versus-time curve from time zero to the last measurable concentration (AUC24h) value was 13.21 ± 6.88 μg·h/mL. After dosing with valsartan 160 mg, the mean Cmax was 4.13 ± 1.49 μg/mL at 1.80 ± 1.53 h, the AUC24h was 26.02 ± 12.07 μg·h/mL. The Cmax and AUC values increased in proportion to the increment in valsartan dose, while the pharmacokinetic parameters of elimination rate constant, half-life, apparent of total clearance, and apparent of volume of distribution were not significantly different between the doses. Valsartan pharmacokinetic analysis fits a one-compartment model with first-order absorption and elimination following a single dose of valsartan 80 mg and 160 mg. In addition, high inter-individual variability was identified in the absorption rate constant. In conclusion, valsartan displays the dose-dependent pharmacokinetics in dogs, and Subsequent quantitative modeling approaches provided detailed pharmacokinetic information of valsartan. The current findings provide useful information in dogs that will aid future development of improved formulations or fixed-dose combinations.

Keywords: dose-dependent, modeling, pharmacokinetics, valsartan

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Authors: Sahin Emrah Amrahov, Fatih Aybar, Serhat Dogan

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In this paper we consider the rule reduct generation problem. Rule Reduct Generation (RG) and Modified Rule Generation (MRG) algorithms, that are used to solve this problem, are well-known. Alternative to these algorithms, we develop Pruning Rule Generation (PRG) algorithm. We compare the PRG algorithm with RG and MRG.

Keywords: rough sets, decision rules, rule induction, classification

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Authors: Emmanuel C. Ngerem

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The ever-increasing depletion of the dominant global form of energy (fossil fuels) calls for the development of sustainable and green alternative energy sources such as bioethanol, biohydrogen, and biodiesel. The production of the major biofuels relies on biomass feedstocks that are mainly derived from edible food crops and some inedible plants. One suitable feedstock with great potential as raw material for biofuel production is microalgal biomass. Despite the tremendous attributes of microalgae as a source of biofuel, their cultivation requires huge volumes of freshwater, thus posing a serious threat to commercial-scale production and utilization of algal biomass. In this study, a multi-media wastewater mixture for microalgae growth was formulated and optimized. Moreover, the obtained microalgae biomass was pre-treated to reduce sugar recovery and was compared with previous studies on microalgae biomass pre-treatment. The formulated and optimized mixed wastewater media for biomass and lipid accumulation was established using the simplex lattice mixture design. Based on the superposition approach of the potential results, numerical optimization was conducted, followed by the analysis of biomass concentration and lipid accumulation. The coefficients of regression (R²) of 0.91 and 0.98 were obtained for biomass concentration and lipid accumulation models, respectively. The developed optimization model predicted optimal biomass concentration and lipid accumulation of 1.17 g/L and 0.39 g/g, respectively. It suggested 64.69% dairy wastewater (DWW) and 35.31% paper and pulp wastewater (PWW) mixture for biomass concentration, 34.21% DWW, and 65.79% PWW for lipid accumulation. Experimental validation generated 0.94 g/L and 0.39 g/g of biomass concentration and lipid accumulation, respectively. The obtained microalgae biomass was pre-treated, enzymatically hydrolysed, and subsequently assessed for reducing sugars. The optimization of microwave pre-treatment of Chlorococcum sp. was achieved using response surface methodology (RSM). Microwave power (100 – 700 W), pre-treatment time (1 – 7 min), and acid-liquid ratio (1 – 5%) were selected as independent variables for RSM optimization. The optimum conditions were achieved at microwave power, pre-treatment time, and acid-liquid ratio of 700 W, 7 min, and 32.33:1, respectively. These conditions provided the highest amount of reducing sugars at 10.73 g/L. Process optimization predicted reducing sugar yields of 11.14 g/L on microwave-assisted pre-treatment of 2.52% HCl for 4.06 min at 700 watts. Experimental validation yielded reducing sugars of 15.67 g/L. These findings demonstrate that dairy wastewater and paper and pulp wastewater that could pose a serious environmental nuisance. They could be blended to form a suitable microalgae growth media, consolidating the potency of microalgae as a viable feedstock for fermentable sugars. Also, the outcome of this study supports the microalgal wastewater biorefinery concept, where wastewater remediation is coupled with bioenergy production.

Keywords: wastewater cultivation, mixture design, lipid, biomass, nutrient removal, microwave, Chlorococcum, raceway pond, fermentable sugar, modelling, optimization

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Authors: Magdalena Barbara Kaziuk, Waldemar Kosiba, Marek Jan Kuzniewski

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Introduction: Vitamin D3 has a proven pleiotropic effect, not only responsible for calcium and phosphate management, but also influencing normal functioning of the whole body. Aim: Evaluation of vitamin D3 resources and its effect on a nutritional status, obesity type and glomerular filtration in kidney transplant recipients. Methods: Group of 152 (81 women and 71 men, average age 47.8 ± 11.6 years) patients with a functioning renal transplant their body composition was assessed using the bioimpendance method (BIA) and anthropometric measurements more than 3 months after the transplant. The nutritional status and the obesity type were determined with the Waist to Height Ratio (WHtR) and the Waist to Hip Ratio (WHR). 25- Hydroxyvitamin D3 (25 (OH)D3) was determined, together with its correlation with the obesity type and the glomerular filtration rate (eGFR) calculated with the MDRD formula. Results: The mean 25 (OH)D3 level was 20.4 ng/ml. 30ng/ml was considered as a minimum correct level 22,7% of patients from the study group were classified to be a correct body weight, 56,7% of participants had an android type and 20,6% had a gynoid type. Significant correlation was observed between 25 (OH)D3 deficiency and abdominal obesity (p < 0.005) in patients. Furthermore, a statistically significant relationship was demonstrated between the 25 (OH)D3 levels and eGFR in patients after a kidney transplant. Patients with an android body type had lower eGFR versus those with the gynoid body type (p=0.004). Conclusions: Correct diet in patients after a kidney transplant determines minimum recommended serum levels of vitamin D3. Excessive fatty tissue, low levels of 25 (OH)D3), may be a predictor for android obesity and renal injury; therefore, correct diet and pharmacological management together with physical activities adapted to the physical fitness level of a patient are necessary.

Keywords: kidney transplantation, glomerular filtration rate, obesity, vitamin D3

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Authors: Ali Gharaee, Mohammad Reza Khosravi Nikou, Bagher Anvaripour, Ali Asghar Mahjoobi

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Soil contamination by petroleum hydrocarbon (PHC) is a major concern facing the oil and gas industry. Particularly, condensate liquids have been found to contaminate soil at gas production sites. The remediation of PHCs is a difficult challenge due to the complex interaction between contaminant and soil. A study has been conducted to enhance degradation of PHCs by Fenton oxidation and using Nanoscale Zero-Valent Iron as catalyst. The various operating conditions such as initial H2O2 concentration, nZVI dosage, reaction time, and initial contamination dose were investigated. Central composite design was employed to optimize and analyze the effect of operational parameters on the PHC removal efficiency. It was found that optimal molar ratio of H2O2/Fe0 was 58 with maximum TPH removal of 84% and 3hr reaction time and initial contaminant concentration was 15g oil /kg soil. Based on the results, combination of Nanoscale ZVI and Fenton has proved to be a promising remedy for contaminated soil.

Keywords: oil contaminated Soil, fenton oxidation, zero valent iron nano-particles

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Authors: Shubham Sharma, Sandra Barkauskaite, Brendan Duffy, Swarna Jaiswal, Amit K. Jaiswal

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Food packaging protects food from temperature, light, and humidity; preserves food and guarantees the safety and the integrity of the food. Advancement in packaging research leads to development of active packaging system with numerous properties such as oxygen scavengers, carbon-dioxide generating systems, antimicrobial active packaging, moisture control packaging, ethylene scavengers etc. In the active packaging, several additives such as essential oils, polyphenols etc. are incorporated into packaging film or within the packaging material to achieve the desired properties. This study investigates the effect on the structural, thermal and functional properties of different poly(lactide) – poly (butylene adipate-co-terephthalate) (PLA-PBAT) blend films incorporated with clove essential oil. The PLA-PBAT films were prepared by a solution casting method and then characterized based on their optical, mechanical properties, surface hydrophobicity, chemical composition, antimicrobial activity against S. aureus and E. coli, and inhibition of biofilm formation of E. coli. Results showed that, the developed packaging film containing clove oil has significant UV-blocking property (80%). However, incorporation of clove oil resulted in reduced transparency and tensile strength of the film as the concentration of clove oil increased. The surface hydrophobicity of packaging film was improved with the increasing concentration of essential oil. Similarly, thickness of the clove oil containing films increased from 36.71 µm to 106.67 µm as the concentration increases. The antimicrobial activity and biofilm inhibition study showed that the clove-incorporated PLA-PBAT composite film was effective against tested bacteria E. coli and S. aureus. This study showed that the PLA-PBAT – Clove oil composite film has significant antimicrobial and UV-blocking properties and can be used as an active food packaging film.

Keywords: active packaging, clove oil, poly(butylene adipate-co-terephthalate), poly(lactide)

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Authors: Vytautas Galvanauskas, Rimvydas Simutis, Donatas Levisauskas, Vykantas Grincas, Renaldas Urniezius

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The paper deals with model-based development and implementation of efficient control strategies for recombinant protein synthesis in fed-batch E.coli cultivation processes. Based on experimental data, a kinetic dynamic model for cultivation process was developed. This model was used to determine substrate feeding strategies during the cultivation. The proposed feeding strategy consists of two phases – biomass growth phase and recombinant protein production phase. In the first process phase, substrate-limited process is recommended when the specific growth rate of biomass is about 90-95% of its maximum value. This ensures reduction of glucose concentration in the medium, improves process repeatability, reduces the development of secondary metabolites and other unwanted by-products. The substrate limitation can be enhanced to satisfy restriction on maximum oxygen transfer rate in the bioreactor and to guarantee necessary dissolved carbon dioxide concentration in culture media. In the recombinant protein production phase, the level of substrate limitation and specific growth rate are selected within the range to enable optimal target protein synthesis rate. To account for complex process dynamics, to efficiently exploit the oxygen transfer capability of the bioreactor, and to maintain the required dissolved oxygen concentration, adaptive control algorithms for dissolved oxygen control have been proposed. The developed model-based control strategies are useful in scale-up of cultivation processes and accelerate implementation of innovative biotechnological processes for industrial applications.

Keywords: adaptive algorithms, model-based control, recombinant E. coli, scale-up of bioprocesses

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Authors: Lukman Ahmad Jamil, Heather M. Wallace

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Introduction: Numerous epidemiological studies have shown a positive as well as negative association and no association in some cases between chronic use of calcium channel blockers and the increased risk of developing cancer. However, these associations were enmeshed with controversies in the absence of laboratory based studies to back up those claims. Aim: The aim of this study was to determine in mechanistic terms the association between the long-term administration of nifedipine and diltiazem and increased risk of developing cancer using the human embryonic kidney (HEK293) cell line. Methods: Cell counting using the Trypan blue dye exclusion and 3-4, 5-Dimethylthiazol-2-yl-2, 5-diphenyl-tetrazolium bromide (MTT) assays were used to investigate the effect of nifedipine and diltiazem on the growth pattern of HEK293 cells. Protein assay using modified Lowry method and analysis of intracellular polyamines concentration using Liquid Chromatography – Tandem Mass Spectrometry (LC-MS) were performed to ascertain the mechanism through which chronic use of nifedipine increases the risk of developing cancer. Results: Both nifedipine and diltiazem significantly increased the proliferation of HEK293 cells dose and time dependently. This proliferative effect after 24, 48 and 72-hour incubation period was observed at 0.78, 1.56 and 25 µM for nifedipine and 0.39, 1.56 and 25 µM for diltiazem, respectively. The increased proliferation of the cells was found to be statistically significantly (p<0.05). Furthermore, the increased proliferation of the cells induced by nifedipine was associated with the increase in the protein content and elevated intracellular polyamines concentration level. Conclusion: The chronic use of nifedipine is associated with increased proliferation of cells with concomitant elevation of polyamines concentration and elevated polyamine levels have been implicated in many malignant transformations and hence, these provide a possible explanation on the link between long term use of nifedipine and development of some human cancers. Further studies are needed to evaluate the cause of this association.

Keywords: cancer, nifedipine, polyamine, proliferation

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Authors: Mantas Sriubas, Kristina Bockute, Darius Virbukas, Giedrius Laukaitis

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In this work, the doped TiO2 (dopants – Ca, Mg) was investigated. The comparison between the physical vapour deposition methods as electron beam vapour deposition and magnetron sputtering was performed and the structural and electrical properties of the formed thin films were investigated. Thin films were deposited on different type of substrates: SiO2, Alloy 600 (Fe-Ni-Cr) and Al2O3 substrates. The structural properties were investigated using Ambios XP-200 profilometer, scanning electron microscope (SEM) Hitachi S-3400N, X-ray energy-dispersive spectroscope (EDS) Quad 5040 (Bruker AXS Microanalysis GmbH), X-ray diffractometer (XRD) D8 Discover (Bruker AXS GmbH) with glancing angles focusing geometry in a 20 – 70° range using the Cu Kα1 λ = 0.1540562 nm radiation). The impedance spectroscopy measurements were performed using Probostat® (NorECs AS) measurement cell in the frequency range from 10-1-106 Hz under reducing and oxidizing conditions in temperature range of 200 °C to 1200 °C. The investigation of the e-beam deposited Ca and Mg doped-TiO2 thin films shows that the thin films are dense without any visible pores and cavities and the thin films grow in zone T according Barna-Adamik SZM. Substrate temperature was kept 600 °C during the deposition and Ts/Tm ≈ 0.32 (substrate temperature (Ts) and coating material melting temperature (Tm)). The surface diffusion is high however, the grain boundary migration is strongly limited at this temperature. This means that structure is inhomogeneous and the columnar structure is mostly visible in the upper part of the films. According to XRD, the increasing of the Ca dopants’ concentration increases the crystallinity of the formed thin films and the crystallites size increase linearly and Ca dopants act as prohibitors. Thin films are comprised of anatase TiO2 phase with an exception of 2 % Ca doped TiO2, where a small peak of Ca arise. In the case of Mg doped-TiO2 the intensities of the XRD peaks decreases with increasing Mg molar concentration. It means that there are less diffraction planes of the particular orientation in thin films with higher impurities concentration. Thus, the crystallinity decreases with increasing Mg concentration and Mg dopants act as inhibitors. The impedance measurements show that the dopants changed the conductivity of the formed thin films. The conductivity varies from 10-3 S/cm to 10-4 S/cm at 800 °C under wet reducing conditions. The microstructure of the magnetron sputtered thin TiO2 films is different comparing to the thin films deposited using e-beam deposition therefore influencing other structural and electrical properties.

Keywords: electrical properties, electron beam deposition, magnetron sputtering, microstructure, titanium dioxide

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Authors: Nirmala Lama

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The construction of high dams has led to significant challenges in managing flow rates discharging over spillways, resulting in cavitation damages on hydraulic surfaces. To address this, aerator devices were designed and installed to promote fore aeration, thereby controlling and mitigating damages caused by cavitation. Consequently, these aerator types, three-dimensional aerators (3DAEs), have demonstrated superior efficiency in introducing forced air into the flow.This research focuses on the installation and evaluation of three-dimensional aerator devices at the high discharge spillway surface. In the laboratory, the air concentration downstream of the hydraulic structures was extensively measured, and the data were analyzed in details.Multiple flow scenarios and structural arrangements of the aerators were adopted for the study. The outcomes of these experiments are listed as In terms of air concentration value, the comparison between 3 DAE (three-dimensional aerator) with offset only and offset with ramp reveals significant differences. The concentration value on the side wall was justified. The side cavity length was found to increase with higher approach Froude numbers and lateral enlargement widths. Furthermore, 3DAE exhibited shorter side cavity lengths compared to three-dimensional aerator devices without ramps (3DAD), a beneficial features for controlling water fins. An empirical formula to express the side cavity length was derived from the measured data. Also, the comparison were made on the basis of water fin formation between the different arrangements of 3D aerators. In conclusion, this research provides valuable insights into the performance of three-dimensional aerators in mitigating cavitation damages and controlling water fins in high dam spillways. The findings offer practical implications for designers and engineers seeking to enhance the efficiency and safety of hydraulic structures subjected to high flow rates.

Keywords: three-dimension aerator, cavity, water fin, air entrainment

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Authors: Sahar B. Ahmed, M. Mostafa Said, Mona I. Mohamed

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Streptozotocin (STZ) caused a significant increase in blood glucose and malondialdehyde (MDA) levels in serum accompanied by a significant decrease in blood reduced glutathione (GSH) and superoxide dismutase (SOD) activities. Also, ALT, AST, albumin and urea were markedly affected by STZ injection. The oral administration of Mango leaves extract (MLE) one hour before STZ injection was significantly improved the blood glucose level, ALT, AST activities, albumin and urea that associated with the regulation of MDA, GSH and SOD levels. The antimicrobial activity of MLE showed a significant inhibitory activity against multidrug resistant gram positive and gram negative bacteria isolated from patients in Egyptian hospitals especially Salmonella typhi and typhimurium. In conclusion, results revealed the antioxidant, hypoglycemic effect and antimicrobial potentials of MLE under investigation. Further studies will be needed to investigate the prolonged period of MLE administration and its possible side effects.

Keywords: aqueous extract of mango leaves, STZ, antioxidant, hypoglycemic effect, antimicrobial potentials.

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Authors: Samuel Odumu Ogana John, Stephen Friday Olukotun, Manny Mathuthu

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Radon-222 (²²²Rn), a naturally occurring radioactive gas, poses potential health risks due to its inhalation and ingestion, especially through drinking water. This study investigates the activity concentration levels of ²²²Rn in 21 brands of bottled water samples collected from the open market in South Africa. The samples were analyzed using a highly sensitive system consisting of the Ionization Chamber AlphaGUARD (PQ 2000), an AquaKIT set, and an AlphaPUMP, ensuring precise measurement of radon activity. The results revealed significant variations in radon concentrations across different brands, with values ranging from 0.062 ± 0.046 Bq/m³ to 0.198 ± 0.286 Bq/mv³, with a mean of 0.118 ± 0.034 Bq/m³. These measurements were then used to estimate the annual effective ingestion dose of radiation for consumers across various age groups based on the guidelines provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The mean effective doses were found to be 4.057 × 10⁻⁴ ± 1.188 × 10⁻⁴ mSv/y for infants (1–2 years), 2.428 × 10⁻⁴ ± 7.111 × 10⁻⁵ mSv/y for children (7–12 years), and 2.058 × 10⁻⁴ ± 6.026 × 10⁻⁵ mSv/y for adults, all of which are below the recommended international safety limits and are comparable to other published studies. These findings suggest that bottled drinking water in South Africa is safe for consumption and does not pose a significant health hazard from ²²²Rn radiation. The study underscores the importance of monitoring radon levels in bottled water to assess the associated radiological health risks, particularly in South Africa, where access to safe drinking water is essential. This research provides baseline data for future regulatory frameworks and policy development and can serve as a valuable reference for bottled water producers. Furthermore, it highlights the need for continued investigation into the regulation and mitigation of radon exposure in drinking water sources throughout the country.

Keywords: Radon-222, activity concentration levels, annual effective ingestion dose, bottled drinking water, South Africa

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Authors: Rahma Goussi, Walid Derbali, Arafet Manaa, Simone Cantamessa, Graziella Berta, Chedly Abdelly, Roberto Barbato

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Salinity is one of the most important abiotic affecting plant growth and productivity worldwide. Photosynthesis, together with cell growth, is among the primary processes to be affected by salinity. Here, we report the effects of salinity stress on the primary processes of photosynthesis in a model halophyte Thellungiella Salsuginea. Plants were cultivated in hydroponic system with different NaCl concentrations (0, 100, 200 and 400 mM) during 2 weeks. The obtained results showed an obvious change in the photosynthetic efficiency of photosystem I (PSI) and phostosytem II (PSII), related to NaCl concentration supplemented to the medium and the stress duration considered. With moderate salinity (100 and 200 mM NaCl), no significant variation was observed in photosynthetic parameters of PSI and PSII and Chl fluorescence whatever the time of stress application. Also, the photosynthesis apparatus Fo, Fm and Fv fluorescence, as well as Fv/Fm were not affected by salt stress. While a significant decrease was observed on quantum yields Y(I), Y(II) and electron transport rate ETR(I), ETR(II) under high salt treatment (400 mM NaCl) with prolonged period (15 days). This reduction is quantitatively compensated by a corresponding increase of energy dissipation Y(NPQ) and a progressive decrease in Fv/Fm under salt treatment. The intensity of the OJIP fluorescence transient decreased with increase in NaCl concentration, with a major effect observed during prolonged period of salt stress. Ultrastructural analysis with Light Microscopy and Transmission Electron Microscopy of T. salsuginea chloroplasts showed some cellular changes, such as the shape of the mesophyll cells and number of chloroplast/cell only under higher NaCl concentration. Salt-stress caused the swelling of thylakoids in T. Salsuginea mesophyll with more accumulation of starch as compared to control plant.

Keywords: fluorescence, halophyte, photosynthesis, salt stress

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Authors: Anastasios Rodis

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Background: Case studies of walkers, climbers, and campers exposed to cold and wet conditions without limb water/windproof protection revealed experiences of muscle weakness and fatigue. It is reasonable to assume that a part of the fatigue could occur due to an alteration in substrate utilization, since reduction of performance in extreme cold conditions, may partially be explained by higher anaerobic glycolysis, reflecting higher carbohydrate oxidation and an increase accumulation rate of blood lactate. The aim of this study was to assess the effects of pre-exercise lower limb cooling on substrate utilization rate during sub-maximal exercise. Method: Six male university students (mean (SD): age, 21.3 (1.0) yr; maximal oxygen uptake (V0₂ max), 49.6 (3.6) ml.min⁻¹; and percentage of body fat, 13.6 (2.5) % were examined in random order after either 30min cold water (12°C) immersion utilized as the cooling strategy up to the gluteal fold, or under control conditions (no precooling), with tests separated by minimum of 7 days. Exercise consisted of 60min cycling at 50% V0₂ max, in a thermoneutral environment of 20°C. Subjects were also required to record a diet diary over the 24hrs prior to the each trial. Means (SD) for the three macronutrients during the 1 day prior to each trial (expressed as a percentage of total energy) 52 (3) % carbohydrate, 31 (4) % fat, and 17 (± 2) % protein. Results: The following responses to lower limb cooling relative to control trial during exercise were: 1) Carbohydrate (CHO) oxidation, and blood lactate (Bₗₐc) concentration were significantly higher (P < 0.05); 2) rectal temperature (Tᵣₑc) was significantly higher (P < 0.05), but skin temperature was significantly lower (P < 0.05); no significant differences were found in blood glucose (Bg), heart rate (HR) and oxygen consumption (V0₂). Discussion: These data suggested that lower limb cooling prior to submaximal exercise will shift metabolic processes from Fat oxidation to CHO oxidation. This shift from Fat to CHO oxidation will probably have important implications in the surviving scenario, since people facing accidental localized cooling of their limbs either through wading/falling in cold water or snow even if they do not perform high intensity activity, they have to rely on CHO availability.

Keywords: exercise in wet conditions, leg cooling, outdoors exercise, substrate utilization

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Authors: Illyas Md Isa, Mohamad Idris Saidin, Mustaffa Ahmad, Norhayati Hashim

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A highly selective and sensitive carbon paste electrode modified with multiwall carbon nanotubes and 2,6–diacetylpyridine-di-(1R)–(-)–fenchone diazine tetracarbonylmolybdenum(0) complex was used for determination of trace amounts of Cu(II) using square wave anodic stripping voltammetry (SWASV). The influences of experimental variables on the proposed electrode such as pH, supporting electrolyte, preconcentration potential and time, and square wave parameters were investigated. Under optimal conditions, the proposed electrode showed a linear relationship with concentration in the range of 1.0 × 10–10 to 1.0 × 10– 6 M Cu(II) with a limit of detection 8.0 × 10–11 M. The relative standard deviation (n = 5) for a solution containing 1.0 × 10– 6 M of Cu(II) was 0.036. The presence of various cations (in 10 and 100-folds concentration) did not interfere. Electrochemical impedance spectroscopy (EIS) showed that the charge transfer at the electrode-solution interface was favourable. The proposed electrode was applied for the determination of Cu(II) in several water samples. Results agreed very well with those obtained by inductively coupled plasma-optical emission spectrometry. The modified electrode was then proposed as an alternative for determination of Cu(II).

Keywords: chemically modified electrode, Cu(II), square wave anodic stripping voltammetry, tetracarbonylmolybdenum(0)

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Authors: Gopal Ji, Priyanka Dwivedi, Shanthi Sundaram, Rajiv Prakash

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Inhibition effect of aqueous Argemone Mexicana root extract (AMRE) on mild steel corrosion in 1 M HCl has been studied by weight loss, Tafel polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Results indicate that inhibition ability of AMRE increases with the increasing amount of the extract. A maximum corrosion inhibition of 94% is acknowledged at the extract concentration of 400 mg L-1. Polarization curves and impedance spectra reveal that both cathodic and anodic reactions are suppressed due to passive layer formation at metal-acid interface. It is also confirmed by SEM micro graphs and FTIR studies. Furthermore, the effects of acid concentration (1-5 M), immersion time (120 hours) and temperature (30-60˚C) on inhibition potential of AMRE have been investigated by weight loss method and electrochemical techniques. Adsorption mechanism is also proposed on the basis of weight loss results, which shows good agreement with Langmuir isotherm.

Keywords: mild steel, polarization, SEM, acid corrosion, EIS, green inhibition

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Authors: Chinumani Choudhury

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Heavy metal contamination is an alarming problem, which poses a serious risk to human health and the surrounding geology. Soils get contaminated with heavy metals due to the un-regularized industrial discharge of the toxic metal-rich effluents. Under such a condition, the remediation of the contaminated sites becomes imperative for a sustainable, safe, and healthy environment. Phytoextraction, which involves the removal of heavy metals from the soil through root absorption and uptake, is a viable remediation technique, which ensures extraction of the toxic inorganic compound available in the soil even at low concentrations. The soil present in the Silghat Region of Assam, India, is mostly contaminated with Zinc (Zn) and Lead (Pb), having concentrations as high as to cause a serious environmental problem if proper measures are not taken. In the present study, an extensive experimental study was carried out to understand the effectiveness of two commonly planted trees in Assam, namely, i) Indian Pennywort and ii) Fenugreek, in the removal of heavy metals from the contaminated soil. The basic characterization of the soil in the contaminated site of the Silghat region was performed and the field concentration of Zn and Pb was recorded. Various long-term laboratory pot tests were carried out by sowing the seeds of Indian Pennywort and Fenugreek in a soil, which was spiked, with a very high dosage of Zn and Pb. The tests were carried out for different concentration of a particular heavy metal and the individual effectiveness in the absorption of the heavy metal by the plants were studied. The concentration of the soil was monitored regularly to assess the rate of depletion and the simultaneous uptake of the heavy metal from the soil to the plant. The amount of heavy metal uptake by the plant was also quantified by analyzing the plant sample at the end of the testing period. Finally, the study throws light on the applicability of the studied plants in the field for effective remediation of the contaminated sites of Assam.

Keywords: phytoextraction, heavy-metals, Indian pennywort, fenugreek

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Authors: L. P. Gomes, G. F. Araújo, Y. M. L. Cordeiro, C. T. Andrade, E. M. Del Aguila, V. M. F. Paschoalin

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The application of nanoscale materials and nanostructures is an emerging area, these since materials may provide solutions to technological and environmental challenges in order to preserve the environment and natural resources. To reach this goal, the increasing demand must be accompanied by 'green' synthesis methods. Chitosan is a natural, nontoxic, biopolymer derived by the deacetylation of chitin and has great potential for a wide range of applications in the biological and biomedical areas, due to its biodegradability, biocompatibility, non-toxicity and versatile chemical and physical properties. Chitosan also presents high antimicrobial activities against a wide variety of pathogenic and spoilage microorganisms. Ultrasonication is a common tool for the preparation and processing of polymer nanoparticles. It is particularly effective in breaking up aggregates and in reducing the size and polydispersity of nanoparticles. High-intensity ultrasonication has the potential to modify chitosan molecular weight and, thus, alter or improve chitosan functional properties. The aim of this study was to evaluate the influence of sonication intensity and time on the changes of commercial chitosan characteristics, such as molecular weight and its potential antibacterial activity against Gram-negative bacteria. The nanoparticles (NPs) were produced from two commercial chitosans, of medium molecular weight (CS-MMW) and low molecular weight (CS-LMW) from Sigma-Aldrich®. These samples (2%) were solubilized in 100 mM sodium acetate pH 4.0, placed on ice and irradiated with an ultrasound SONIC ultrasonic probe (model 750 W), equipped with a 1/2" microtip during 30 min at 4°C. It was used on constant duty cycle and 40% amplitude with 1/1s intervals. The ultrasonic degradation of CS-MMW and CS-LMW were followed up by means of ζ-potential (Brookhaven Instruments, model 90Plus) and dynamic light scattering (DLS) measurements. After sonication, the concentrated samples were diluted 100 times and placed in fluorescence quartz cuvettes (Hellma 111-QS, 10 mm light path). The distributions of the colloidal particles were calculated from the DLS and ζ-potential are measurements taken for the CS-MMW and CS-LMW solutions before and after (CS-MMW30 and CS-LMW30) sonication for 30 min. Regarding the results for the chitosan sample, the major bands can be distinguished centered at Radius hydrodynamic (Rh), showed different distributions for CS-MMW (Rh=690.0 nm, ζ=26.52±2.4), CS-LMW (Rh=607.4 and 2805.4 nm, ζ=24.51±1.29), CS-MMW30 (Rh=201.5 and 1064.1 nm, ζ=24.78±2.4) and CS-LMW30 (Rh=492.5, ζ=26.12±0.85). The minimal inhibitory concentration (MIC) was determined using different chitosan samples concentrations. MIC values were determined against to E. coli (106 cells) harvested from an LB medium (Luria-Bertani BD™) after 18h growth at 37 ºC. Subsequently, the cell suspension was serially diluted in saline solution (0.8% NaCl) and plated on solid LB at 37°C for 18 h. Colony-forming units were counted. The samples showed different MICs against E. coli for CS-LMW (1.5mg), CS-MMW30 (1.5 mg/mL) and CS-LMW30 (1.0 mg/mL). The results demonstrate that the production of nanoparticles by modification of their molecular weight by ultrasonication is simple to be performed and dispense acid solvent addition. Molecular weight modifications are enough to provoke changes in the antimicrobial potential of the nanoparticles produced in this way.

Keywords: antimicrobial agent, chitosan, green production, nanoparticles

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Authors: Yonosuke Murayama

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We have developed and studied a metastable beta Ti alloy, which shows super-elasticity and low Young’s modulus according to the phase stability of its beta phase. The super-elasticity and low Young’s modulus are required in a wide range of applications in various industrial fields. For example, the metallic implant with low Young’s modulus and non-toxicity is desirable because the large difference of Young’s modulus between the human bone and the implant material may cause a stress-shielding phenomenon. We have investigated the role of Sn and Al in metastable beta Ti-Cr-Sn, Ti-Cr-Al, Ti-V-Sn, and Ti-V-Al alloys. The metastable beta Ti-Cr-Sn, Ti-Cr-Al, Ti-V-Sn, and Ti-V-Al alloys form during quenching from the beta field at high temperature. While Cr and V act as beta stabilizers, Sn and Al are considered as elements to suppress the athermal omega phase produced during quenching. The athermal omega phase degrades the properties of super-elasticity and Young’s modulus. Although Al and Sn as single elements are considered as an alpha stabilizer and neutral, respectively, Sn and Al acted also as beta stabilizers when added simultaneously with beta stabilized element of Cr or V in this experiment. The quenched microstructure of Ti-Cr-Sn, Ti-Cr-Al, Ti-V-Sn, and Ti-V-Al alloys shifts from martensitic structure to beta single-phase structure with increasing Cr or V. The Young’s modulus of Ti-Cr-Sn, Ti-Cr-Al, Ti-V-Sn, and Ti-V-Al alloys decreased and then increased with increasing Cr or V, each showing its own minimum value of Young's modulus respectively. The composition of the alloy with the minimum Young’s modulus is a near border composition where the quenched microstructure shifts from martensite to beta. The border composition of Ti-Cr-Sn and Ti-V-Sn alloys required only less amount of each beta stabilizer, Cr or V, than Ti-Cr-Al and Ti-V-Al alloys. This indicates that the effect of Sn as a beta stabilizer is stronger than Al. Sn and Al influenced the competitive relation between stress-induced martensitic transformation and slip deformation. Thus, super-elastic properties of metastable beta Ti-Cr-Sn, Ti-Cr-Al, Ti-V-Sn, and Ti-V-Al alloys varied depending on the alloyed element, Sn or Al.

Keywords: metastable beta Ti alloy, super-elasticity, low Young’s modulus, stress-induced martensitic transformation, beta stabilized element

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Authors: M. F. Mamabolo

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Mining activities are identified as the most significant source of heavy metal contamination in river basins, due to inadequate disposal of mining waste thus resulting in acid mine drainage. Waste materials generated from gold mining and processing have severe and widespread impacts on water resources. Therefore, a total of 30 water samples were collected from Fig Tree Creek, Kaapriver, Sheba mine stream & Sauid kaap river to investigate the impact of gold mines on the Kaap River system. Physicochemical parameters (pH, EC and TDS) were taken using a BANTE 900P portable water quality meter. The concentration of Fe, Cu, Co, and SO₄²⁻ in water samples were analysed using Inductively Coupled Plasma-Mass spectrophotometry (ICP-MS) at 0.01 mg/L. The results were compared to the regulatory guideline of the World Health Organization (WHO) and the South Africa National Standards (SANS). It was found that Fe, Cu and Co were below the guideline values while SO₄²⁻ detected in Sheba mine stream exceeded the 250 mg/L limit for both seasons, attributed by mine wastewater. SO₄²⁻ was higher in wet season due to high evaporation rates and greater interaction between rocks and water. The pH of all the streams was within the limit (≥5 to ≤9.7), however EC of the Sheba mine stream, Suid Kaap River & where the tributary connects with the Fig Tree Creek exceeded 1700 uS/m, due to dissolved material. The TDS of Sheba mine stream exceeded 1000 mg/L, attributed by high SO₄²⁻ concentration. While the tributary connecting to the Fig Tree Creek exceed the value due to pollution from household waste, runoff from agriculture etc. In conclusion, the water from all sampled streams were safe for consumption due to low concentrations of physicochemical parameters. However, elevated concentration of SO₄²⁻ should be monitored and managed to avoid water quality deterioration in the Kaap River system.

Keywords: Kaap river system, mines, heavy metals, sulphate

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Authors: Z. Asadgol, A. Nadali, H. Arfaeinia, M. Khalifeh Gholi, R. Fateh, M. Fahiminia

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The present investigation was conducted to detect the type and concentrations of bacterial and fungal bioaerosols in one room (bedroom) of each selected residential building located in different regions of Qom during February 2015 (n=9) to July 2016 (n=11). Moreover, we evaluated the efficiency of negative air ions (NAIs) in bioaerosol reduction in indoor air in residential buildings. In the first step, the mean concentrations of bacterial and fungal in nine sampling sites evaluated in winter were 744 and 579 colony forming units (CFU)/m³, while these values were 1628.6 and 231 CFU/m³ in the 11 sampling sites evaluated in summer, respectively. The most predominant genera between bacterial and fungal in all sampling sites were detected as Micrococcus spp. and Staphylococcus spp. and also, Aspergillus spp. and Penicillium spp., respectively. The 95% and 45% of sampling sites have bacterial and fungal concentrations over the recommended levels, respectively. In the removal step, we achieved a reduction with a range of 38% to 93% for bacterial genera and 25% to 100% for fungal genera by using NAIs. The results suggested that NAI is a highly effective, simple and efficient technique in reducing the bacterial and fungal concentration in the indoor air of residential buildings.

Keywords: bacterial, fungal, negative air ions (NAIs), indoor air, Iran

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Authors: Shraddha Srivastava, N. K. Painuly, S. P. Mishra, Navin Singh, Muhsin Punchankandy, Kirti Srivastava, M. L. B. Bhatt

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Various optimization methods used in interstitial brachytherapy are based on dwell positions and dwell weights alteration to produce dose distribution based on the implant geometry. Since these optimization schemes are not anatomy based, they could lead to deviations from the desired plan. This study was henceforth carried out to compare anatomy-based Inverse Planning Simulated Annealing (IPSA) optimization technique with graphical and geometrical optimization methods in interstitial high dose rate brachytherapy planning of cervical carcinoma. Six patients with 12 CT data sets of MUPIT implants in HDR brachytherapy of cervical cancer were prospectively studied. HR-CTV and organs at risk (OARs) were contoured in Oncentra treatment planning system (TPS) using GYN GEC-ESTRO guidelines on cervical carcinoma. Three sets of plans were generated for each fraction using IPSA, graphical optimization (GrOPT) and geometrical optimization (GOPT) methods. All patients were treated to a dose of 20 Gy in 2 fractions. The main objective was to cover at least 95% of HR-CTV with 100% of the prescribed dose (V100 ≥ 95% of HR-CTV). IPSA, GrOPT, and GOPT based plans were compared in terms of target coverage, OAR doses, homogeneity index (HI) and conformity index (COIN) using dose-volume histogram (DVH). Target volume coverage (mean V100) was found to be 93.980.87%, 91.341.02% and 85.052.84% for IPSA, GrOPT and GOPT plans respectively. Mean D90 (minimum dose received by 90% of HR-CTV) values for IPSA, GrOPT and GOPT plans were 10.19 ± 1.07 Gy, 10.17 ± 0.12 Gy and 7.99 ± 1.0 Gy respectively, while D100 (minimum dose received by 100% volume of HR-CTV) for IPSA, GrOPT and GOPT plans was 6.55 ± 0.85 Gy, 6.55 ± 0.65 Gy, 4.73 ± 0.14 Gy respectively. IPSA plans resulted in lower doses to the bladder (D₂

Keywords: cervical cancer, HDR brachytherapy, IPSA, MUPIT

Procedia PDF Downloads 191

Authors: Katie Emerson, Sara Perez-Ojalvo, Jim Komorowski, Danielle Greenberg

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The purpose of this study was to evaluate arginase activity levels in response to combinations of an inositol-stabilized arginine silicate (ASI; Nitrosigine®), L-arginine, and Inositol. Arginine acts as a vasodilator that promotes increased blood flow resulting in enhanced delivery of oxygen and nutrients to the brain and other tissues. ASI alone has been shown to improve performance on cognitive tasks. Arginase, found in human serum, catalyzes the conversion of arginine to ornithine and urea, completing the last step in the urea cycle. Decreasing arginase levels maintains arginine and results in increased nitric oxide production. This study aimed to determine the most effective combination of ASI, L-arginine and inositol for minimizing arginase levels and therefore maximize ASI’s effect on cognition. Serum was taken from untreated healthy donors by separation from clotted factors. Arginase activity of serum in the presence or absence of test products was determined (QuantiChrom™, DARG-100, Bioassay Systems, Hayward CA). The remaining ultra-filtrated serum units were harvested and used as the source for the arginase enzyme. ASI alone or combined with varied levels of Inositol were tested as follows: ASI + inositol at 0.25 g, 0.5 g, 0.75 g, or 1.00 g. L-arginine was also tested as a positive control. All tests elicited changes in arginase activity demonstrating the efficacy of the method used. Adding L-arginine to serum from untreated subjects, with or without inositol only had a mild effect. Adding inositol at all levels reduced arginase activity. Adding 0.5 g to the standardized amount of ASI led to the lowest amount of arginase activity as compared to the 0.25g 0.75g or 1.00g doses of inositol or to L-arginine alone. The outcome of this study demonstrates an interaction of the pairing of inositol with ASI on the activity of the enzyme arginase. We found that neither the maximum nor minimum amount of inositol tested in this study led to maximal arginase inhibition. Since the inhibition of arginase activity is desirable for product formulations looking to maintain arginine levels, the most effective amount of inositol was deemed preferred. Subsequent studies suggest this moderate level of inositol in combination with ASI leads to cognitive improvements including reaction time, executive function, and concentration.

Keywords: arginine, inositol, arginase, cognitive benefits

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Authors: Ekaterina S. Marchenko, Gulsharat A. Baigonakova, Kirill M. Dubovikov, Igor A. Khlusov

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NiTi alloys combine biomechanical and biochemical properties. This makes them a perfect candidate for medical applications. However, there is a serious problem with these alloys, such as the release of Ni from the matrix. Ni ions are known to be toxic to living tissues and leach from the matrix into the surrounding implant tissues due to corrosion after prolonged use. To prevent the release of Ni ions, corrosive strong coatings are usually used. Titanium nitride-based coatings are perfect corrosion inhibitors and also have good bioactive properties. However, there is an opportunity to improve the biochemical compatibility of the surface by depositing another layer. This layer can consist of elements such as calcium and phosphorus. The Ca and P ions form different calcium phosphate phases, which are present in the mineral part of human bones. We therefore believe that these elements must promote osteogenesis and osteointegration. In view of the above, the aim of this study is to investigate the effect of crystallinity on the biocompatibility of a two-layer coating deposited on NiTi substrate by sputtering. The first step of the research, apart from the NiTi polishing, is the layer-by-layer deposition of Ti-Ni-Ti by magnetron sputtering and the subsequent synthesis of this composite in an N atmosphere at 900 °C. The total thickness of the corrosion resistant layer is 150 nm. Plasma assisted RF sputtering was then used to deposit a bioactive film on the titanium nitride layer. A Ca-P powder target was used to obtain such a film. We deposited three types of Ca-P layers with different crystallinity and compared them in terms of cytotoxicity. One group of samples had no Ca-P coating and was used as a control. We obtained different crystallinity by varying the sputtering parameters such as bias voltage, plasma source current and pressure. XRD analysis showed that all coatings are calcium phosphate, but the sample obtained at maximum bias and plasma source current and minimum pressure has the most intense peaks from the coating phase. SEM and EDS showed that all three coatings have a homogeneous and dense structure without cracks and consist of calcium, phosphorus and oxygen. Cytotoxic tests carried out on three types of samples with Ca-P coatings and a control group showed that the control sample and the sample with Ca-P coating obtained at maximum bias voltage and plasma source current and minimum pressure had the lowest number of dead cells on the surface, around 11 ± 4%. Two other types of samples with Ca-P coating have 40 ± 9% and 21 ± 7% dead cells on the surface. It can therefore be concluded that these two sputtering modes have a negative effect on the corrosion resistance of the whole samples. The third sputtering mode does not affect the corrosion resistance and has the same level of cytotoxicity as the control. It can be concluded that the most suitable sputtering mode is the third with maximum bias voltage and plasma source current and minimum pressure.

Keywords: calcium phosphate coating, cytotoxicity, NiTi alloy, two-layer coating

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