The present work addresses the printed sand mold thickness effect on the solidification process of a eutectic aluminum-silicon alloy (AlSi13). Several sand mold thicknesses (varying from 3 to 30 mm) ...are numerically studied using Quikcast® software. The study shows that the solidification time decreases when the sand thickness of mold increases. It is accelerated by more than 40% when the sand mold thickness increases from 3 to 30 mm. The numerical simulations are coupled with experiments. Indeed, the 3D sand printing process is used to fabricate molds presenting different thicknesses of 5 mm and 30 mm, respectively. In addition, the same printing parameters are applied for producing all sand molds. The comparison between both numerical and experimental results shows the same tendency according to the sand mold thickness. The results indicate that increasing the sand mold thickness from 5 to 30 mm allows to accelerate the solidification by 17% and 18.6%, respectively, in the numerical and experimental results. A finer microstructure is obtained when reducing the solidification time, which enhances the hardness of casting properties.
Knowing the thermo-mechanical history of a part during its processing is essential to master the final properties of the product. During forming processes, several parameters can affect it. The ...development of a surrogate model makes it possible to access history in real time without having to resort to a numerical simulation. We restrict ourselves in this study to the cooling phase of the casting process. The thermal problem has been formulated taking into account the metal as well as the mould. Physical constants such as latent heat, conductivities and heat transfer coefficients has been kept constant. The problem has been parametrized by the coolant temperatures in five different cooling channels. To establish the offline model, multiple simulations are performed based on well-chosen combinations of parameters. The space-time solution of the thermal problem has been solved parametrically. In this work we propose a strategy based on the solution decomposition in space, time, and parameter modes. By applying a machine learning strategy, one should be able to produce modes of the parametric space for new sets of parameters. The machine learning strategy uses either random forest or polynomial fitting regressors. The reconstruction of the thermal solution can then be done using those modes obtained from the parametric space, with the same spatial and temporal basis previously established. This rationale is further extended to establish a model for the ignored part of the physics, in order to describe experimental measures. We present a strategy that makes it possible to calculate this ignorance using the same spatio-temporal basis obtained during the implementation of the numerical model, enabling the efficient construction of processing hybrid twins.
•Essential oils are a mixture of bioactive volatile compounds.•Essential oils are potent antimicrobial and antioxidant agents.•Essential oils have the potential to be used as a food ...preservative.•There are limitations to the use of essential oils as food preservative.
Essential oils (EOs) are natural, volatile and aromatic liquids extracted from special plants. EOs are complex mixture of secondary metabolites (terpenes, phenolic compounds, alcohol). EOs possess a wide range of biological activities including antioxidant, antimicrobial and anti-inflammatory ones. Particularly, EOs exhibit pronounced antibacterial and food preservative properties that represent a real potential for the food industry. Numerous EOs have the potential to be used as a food preservative for meat and meat products, vegetables and fruits as well as for dairy products. The main obstacles for using EOs as food preservatives are their safety limits, marked organoleptic effects and possible contamination by chemical products such as pesticides. This review aims to provide an overview of current knowledge about EOs food preservative properties with special emphasis on their antibacterial activities and to support their uses as natural, eco-friendly, safe and easily biodegradable agents for food preservation.
This work focuses on the variability of
(Forssk.) Webb bioactive compounds as a function of the plant cycle. The main results showed that it exhibited the highest percentage of polyunsaturated fatty ...acids, along with superior levels of vitamin C and total phenolic compounds (66.49%, 645.6 mg·100 g
¹ FW and 23.9 mg GAE·g
¹, respectively) at the vegetative stage. Instead, at the flowering and mature fruiting stages,
(Forssk.) Webb exhibited notable contents of proline (25.4 μmol·g
¹ DW) and carotenoids (27.2 μg·g
¹ FW), respectively. The gathered data concerning the antioxidant activity highlighted the effectiveness of the vegetative stage in comparison to the other periods. Actually, IC
and EC
values of the hydromethanolic extract obtained from the plant shoots at the vegetative stage were of 23, 380, 410, 1160 and 960 μg·mL
(DPPH
and ABTS
radicals scavenging activity, reducing power, chelating power and β-carotene bleaching activity, respectively). Furthermore, the four studied stages showed appreciable antibacterial capacities against human pathogens with a higher efficiency of the vegetative stage extract. Finally, the LC-DAD-ESI/MS
analysis revealed the predominance of isoflavonoids as main class of phenolic compounds and demonstrates that individual phenolic biosynthesis was clearly different as a function of plant growth. These findings highlight that reaching the optimum efficiency of
(Forssk.) Webb is closely linked to the physiological stage.
The fractionation of the methanolic extract (MeOH-E) of Retama raetam (Forssk.) Webb & Berthel and further analysis by thin layer chromatography resulted in four fractions (F1, F2, F3 and F4) that, ...in parallel with the MeOH-E, were screened for antioxidant, cytotoxic, antidiabetic and antibacterial properties. In addition, chemical characterization of their bioactive molecules was performed using LC-DAD-ESI/MSn. The results indicated that F3 was the most promising regarding antioxidant and cytotoxicity abilities, possibly due to its richness in flavonoids class, particularly isoflavones. In turn, F1 was characterized by the presence of the most polar compounds from MeOH-E (organic acids and piscidic acid) and showed promising abilities to inhibit α-amylase, while F4, which contained prenylated flavonoids and furanoflavonoids, was the most active against the tested bacteria. The gathered results emphasize the distinct biological potentials of purified fractions of Retama raetam.
Iron (Fe) deficiency causes great disturbances to plant growth, productivity and metabolism. This study investigated the effect of bicarbonate-induced Fe deficiency on Foeniculum vulgare (Mill) ...growth, nutrient uptake, the accumulation of secondary metabolites and the impact on bioactivities. When grown under indirect Fe deficiency conditions (+Fe +Bic), the plants decreased their total mass, an effect that was clearly evident in shoots (−28%). Instead, roots were the main organ affected regarding variations in the phenolic profile and their respective functionalities. Hydromethanolic extracts from bicarbonate-treated roots had a remarkable increase in the levels of phenolic compounds, both of flavonoids (isoquercetin and isorhamnetin) and phenolic acids (gallic acid, chlorogenic acid, syringic acid, ferulic acid, caffeic acid and trans-cinnamic acid), when compared to equivalent extracts from control plants. In addition, they exhibited higher scavenging abilities of DPPH•, NO•, RO2•, as well as inhibitory capacities towards the activity of lipoxygenase (LOX), xanthine oxidase (XO) and acetylcholinesterase (AChE). The overall results suggest that fennel species may modulate secondary metabolites metabolism to fight damages caused by iron deficiency.
Nanopeening treatment was applied to the AISI 420 steel to decrease its sensitivity to tribocorrosion damage. The microstructural investigation highlighted that the nanopeening treatment led to high ...plastic deformation and a nanostructured surface layer with a 110 µm depth. In order to study the combined effect of corrosion and mechanical wear, tribocorrosion tests were performed on non-treated and nanopeened samples in boric acid and lithium hydroxide solutions, considering both continuous and intermittent sliding. It was found that the AISI 420 steel is sensitive to the synergy between mechanical friction and electrochemical corrosion with the dominance of abrasive wear. Adhesive wear was also detected in the wear track. Indeed, the mechanical wear was pronounced under intermittent sliding because of hard wear debris generation from the repassivated layer during rotating time. The nanopeening treatment led to enhanced mechanical performance and corrosion properties. Such improvement could be explained by the high plastic deformation resulting in the nano-structuration of grains and the increasing hardness of AISI 420 steel.
Discovering new antioxidant agents and optimizing their processing is a necessity to treat skin diseases. The assessment of quality and antioxidant activity of topical formulations based on ...5,8-dihydroxy-1,4-naphthoquinone (M1) and 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (M2) was carried out for the first time for this purpose. Stability studies including evaluation of pH, viscosity, microscopic observation, and microbiological quality were determined. M1 and M2 were examined for their antioxidant capacities after their incorporation into bigels. Obtained data suggested that BG-M1 and BG-M2 have a good quality, a natural pH of the skin (4.5–6.0), and no sign of microbial development. Sensory analysis was also performed, and no negative assessment of unpleasant bigel properties was found. M1 and M2 have shown antioxidant activity toward DPPH radical (data are expressed as IC
50
), 19 × 10
−3
mg/mL for M1 and 35 × 10
−3
mg/mL for M2, respectively. After their formulations, they have maintained this ability, for BG-M1 = 3.0 and BG-M2 = 1.1 mg/mL. Also, they demonstrated interesting ABTS scavenging with 1.5 × 10
−3
and 2.5 × 10
−3
mg/mL for M1 and M2, respectively. They kept this potential after formulation, since, BG-M1 = 1.7 mg/mL and BG-M2 = 4.9 mg/mL. Likewise, pure molecules revealed notable β-carotene bleaching inhibition (0.3 and 0.1 mg/mL for M1 and M2, respectively), which was maintained after their formulation into bigels (2.9 and 10.3 mg/mL for BG-M1 and BG-M2, respectively). These developed bigels maintaining the antioxidant potential of M1 and M2 could be used as the provision of a barrier to protect skin.
•The effects of K+ deficiency were investigated on Sulla carnosa plants.•Growth of vegetative organs was decreased by K+ deficiency.•Photosynthetic gas exchange and pigment contents were affected by ...low K+ conditions.•S. carnosa was able to modulate the metabolism of secondary metabolites and their antioxidant activity.
The effects of potassium (K+) deficiency were investigated in Sulla carnosa plants. Plants were grown hydroponically for one month in K+-sufficient (6mMK+, Control) and K+-deficient (60μmK+) solutions inside the greenhouse in Biotechnology Center of Borj Cedria, Tunisia. Growth, water status, pigment contents, photosynthetic gas exchange, photosystem II (PSII) photochemistry and leaf principal secondary metabolites (polyphenols, flavonoids, and condensed tannins), and their antioxidant properties (DPPH (1.1-diphenyl-2-picrylhydrazyl) scavenging capacity, ferric reducing power, chelating effect on ferrous ions, and β-carotene bleaching test) were determined. Growth of vegetative organs was decreased by some 50% by K+ deficiency with stems more affected (−68%) than roots (−42%) and leaves (−45%). Water content decreased in the three vegetative organs. Photosynthetic gas exchange and pigment contents were affected by low K+ conditions. In contrast to condensed tannins which remained constant, total polyphenols and flavonoids contents increased under K+ deficiency (by 62.7 and 14.5%, respectively). Furthermore, total antioxidant activity increased by 33.5% compared to control plants. Except for β-carotene bleaching test that increased, DPPH scavenging capacity, ferric reducing antioxidant power, and chelating effect on ferrous ions decreased owing to K+ deficiency. An increased and/or de novo synthesis of individual polyphenols was also observed by RP-HPLC analysis. As a whole, these data suggest that S. carnosa was able to modulate the metabolism of secondary metabolites and their antioxidant activity under conditions favouring reactive oxygen species (ROS) production in order to minimize the deleterious effects of these oxygen species.
Salinity and K+ deficiency are two environmental constraints that generally occur simultaneously under field conditions, resulting in severe limitation of plant growth and productivity. The present ...study aimed at investigating the effects of salinity, either separately applied or in combination with K+ deficiency, on growth, photosynthetic performance, secondary metabolites content, and related antioxidant capacity in Sulla carnosa. Seedlings were grown hydroponically under sufficient (6000 μM) or low (60 μM) K+ supply with 100 mM NaCl (C + S and D + S treatments, respectively). Either alone or combined with K+ deficiency, salinity significantly restricted the plant growth. K+ deficiency further increased salt impact on the photosynthetic activity of S. carnosa, but this species displayed mechanisms that play a role in protecting photosynthetic machinery (including non photochemical quenching and antioxidant activity). In contrast to plants subjected to salt stress alone, higher accumulation of phenolic compounds was likely related to antioxidative defence mechanism in plants grown under combined effects of two stresses. As a whole, these data suggest that K+ deficiency increases the deleterious effects of salt stress. The quantitative and qualitative alteration of phenolic composition and the enhancement of related antioxidant capacity may be of crucial significance for S. carnosa plants growing under salinity and K+ deficient conditions.
•The effects of salinity alone or in combination with K+ deficiency were investigated in Sulla carnosa plants.•K+ supply influences growth and photosynthetic activity.•Phenolic composition and their antioxidant capacity were modulated by salinity and K+ deficiency.
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