Water Agitation Research Articles

Performance enhancement of solar still desalination using sound agitation and condensation: A comparative study

This research work focuses on the assessment of the CSS and the newly developed Sound Agitation with Condenser Solar Still (SACSS) for water desalination. Field studies were carried out in Coimbatore city in the southern part of India in the month of March 2024. The SACSS incorporated a 40 W speaker for water agitation at 110 Hz, a fan and a condenser unit. The values of the solar radiation, temperature distributions, heat transfer coefficients, energy fractions, yield, efficiency, and cost per liter were recorded and evaluated. Findings show that the SACSS performs much better than the CSS. The SACSS reached a maximum water temperature of 66 °C, a maximum yield of 0.38 kg/m²·h, a peak efficiency of 82 %, and a cost per liter of 1.16 Rs/L, compared to 64 °C, 0.26 kg/m²·h, 62 %, and 1.44 Rs/L for the CSS. The changes in SACSS enhanced thermal control and distillation effectiveness, particularly during high solar intensity.

Natural variation in timing of egg hatching, response to water agitation, and bidirectional selection of early and late hatching strains of the malaria mosquito Anopheles gambiae sensu lato

BackgroundEggs of anopheline mosquitoes hatch within a few days of laying and require high levels of humidity to survive. Assessing natural variation in egg hatching and its environmental and genetic determinants in sibling species of the malaria vector Anopheles gambiae s.l. is important for understanding their adaptation to variable aquatic habitats. Crucially, it can also inform insectary rearing practices toward the optimization of mosquito production for genetic vector control strategies.MethodsHatching rates and timing of egg hatching in long-established and recently colonized strains of An. gambiae s.s, Anopheles arabiensis, and Anopheles coluzzii, were compared under still water conditions (26 ℃) and with cold (4 ℃) and (15 ℃) water agitation regimes. Next, early and late hatching strains of the recently colonized An. coluzzii VK colony were generated through bidirectional selection for 18–23 generations to detect a genetic component for this trait.ResultsHatching rates differed significantly between species and treatments. The older An. arabiensis Senn and An. gambiae s.s. Kisumu strains had the highest proportion of hatching and preferred the nonagitation treatment at 26 °C. In contrast, the more recently colonized An. coluzzii VK and An. arabiensis Rufisque strains had lower overall hatching success but responded strongly to agitation at 4 °C, while the An. coluzzii Mopti strain did not significantly respond to water agitation. In all strains, eggs hatching started at day 2 and continued till day 5 in the older strains, whilst it was more staggered and extended up to day 6 in the younger strains. Bidirectional selection for early and late hatching over many generations resulted in early hatching selected strains with eggs hatching 2–3 days earlier than in late hatching ones indicating a significant heritable component for these traits.ConclusionsWater agitation and temperature and age of colonization are likely important determinants of egg hatching in natural An. gambiae s.l. populations. Current rearing protocols systematically select for fast hatching and result in the progressive loss of staggered egg hatching in older laboratory strains. The selection of novel slow-hatching strains may prove instrumental to enable the mass production, shipping, and release of Anopheles mosquitoes across Africa as part of genetic vector control programs.Graphical

Effects of Light and Water Agitation on Hatching Processes in False Clownfish Amphiprion ocellaris.

False clownfish (Amphiprion ocellaris) employ a hatching strategy regulated by environmental cues, wherein parents provide water flow to encourage embryos to hatch after sunset on the hatching day. Despite previous studies demonstrating the necessity of complete darkness and water agitation for hatching, the regulatory mechanisms underlying these environmental cues remain elusive. This study aimed to investigate how darkness and water agitation affect the secretion of hatching enzymes and the hatching movements of embryos in false clownfish. Assessment of chorion digestion and live imaging of Ca2+ in hatching glands using GCaMP6s, a Ca2+ indicator, revealed that darkness stimulation triggers the secretion of hatching enzymes by increasing Ca2+ levels in hatching gland cells. On the other hand, water agitation primarily stimulated hatching movements in embryos, which led to the rupture of their egg envelopes. These results suggest that changes in light environments following sunset induce embryos to secrete hatching enzymes and that water agitation provided by parents stimulates hatching movements. These responses to environmental cues, light and water agitation, contribute to the rapid and synchronous hatching in false clownfish.

Uranium accumulation in environmentally relevant microplastics and agricultural soil at acidic and circumneutral pH

The co-occurrence of microplastics (MPs) with potentially toxic metals in the environment stresses the need to address their physicochemical interactions and the potential ecological and human health implications. Here, we investigated the reaction of aqueous U with agricultural soil and high-density polyethylene (HDPE) through the integration of batch experiments, microscopy, and spectroscopy. The aqueous initial concentration of U (100 μM) decreased between 98.6 and 99.2 % at pH 5 and between 86.2 and 98.9 % at pH 7.5 following the first half hour of reaction with 10 g of soil. In similar experimental conditions but with added HDPE, aqueous U decreased between 98.6 and 99.7 % at pH 5 and between 76.1 and 95.2 % at pH 7.5, suggesting that HDPE modified the accumulation of U in soil as a function of pH. Uranium-bearing precipitates on the cracked surface of HDPE were identified by SEM/EDS after two weeks of agitation in water at both pH 5 and 7.5. Accumulation of U on the near-surface region of reacted HDPE was confirmed by XPS. Our findings suggest that the precipitation of U was facilitated by the weathering of the surface of HDPE. These results provide insights about surface-mediated reactions of aqueous metals with MPs, contributing relevant information about the mobility of metals and MPs at co-contaminated agricultural sites.

Medium-high density soft micrites: Impact of microstructural features on state and compressibility

Three soft rock facies of the Middle Globigerina Limestone (MGL) from Malta, of mineralogical composition and index properties similar to some medium-high density Chalk facies, are disaggregated through prolonged agitation in water, to create reconstituted samples. The significant activity of their clay-sized calcite grains can impart a medium-high plasticity. SEM analyses of natural and reconstituted samples show the natural bonding as interlock, possibly induced by cohesive clay-sized calcite grains during the sediment compaction. Micro-analyses and compression test data also show that local calcite crystal over-growth under burial has reduced further the soft rock porosity, making it lower than that of the reconstituted material one-dimensionally compressed to the geological preconsolidation pressure. Nonetheless, the low stress sensitivity of natural MGL suggests that this interlock bonding does not strengthen much the material with respect to the highly compressed reconstituted soil. The natural MGL is of very low permeability, which reduces further with compression. Concurrently, the soft rock creep coefficient increases, reaching values far above those typical for clays. The microstructural features and the mechanical properties of the different MGL facies are shown to be sensitive to clay mineral content.

Impact of plasma-activated water on the supramolecular structure and functionality of small and large starch granules

Hydrothermal (HMT) and water agitation (WA) treatments using plasma-activated water (PAW) were employed as sustainable methods to modify the molecular and functional performance of small (rice) and large (potato) starch granules. HMT-PAW and WA-PAW treatments resulted in etched and damaged granular surfaces that rearranged the long and short-range crystallinity of the modified starches. Both treatments seemed to predominantly occur in the amorphous region of the rice starch and the crystalline regions of the potato starch, changing the crystallinity values from 22.9 and 14.8 % to 31.8 and 10.4 %, respectively. Thus, the level of the arrangement of chains reached after PAW treatment decreased the ability of rice starch granules to swell (16 to 9 %) and leach out starch molecules from the granules (4.5 to 1.3 %), decreasing the viscosity and pasting profiles as indicated by n and k values. Opposite behavior was observed in the modified potato starches since starch components leached out to a higher extent (1.7 to 5.4 %). The results showed that HMT and WA treatments using PAW are feasible eco-friendly methods for modifying starch granules without chemical reagents. These modified starches could be suitable as functional ingredients or biopolymeric matrices for the food and packaging industry.

Molecular simulations reveal that heterogeneous ice nucleation occurs at higher temperatures in water under capillary tension

Abstract. Heterogeneous ice nucleation is thought to be the primary pathway for the formation of ice in mixed-phase clouds, with the number of active ice-nucleating particles (INPs) increasing rapidly with decreasing temperature. Here, molecular-dynamics simulations of heterogeneous ice nucleation demonstrate that the ice nucleation rate is also sensitive to pressure and that negative pressure within supercooled water shifts freezing temperatures to higher temperatures. Negative pressure, or tension, occurs naturally in water capillary bridges and pores and can also result from water agitation. Capillary bridge simulations presented in this study confirm that negative Laplace pressure within the water increases heterogeneous-freezing temperatures. The increase in freezing temperatures with negative pressure is approximately linear within the atmospherically relevant range of 1 to −1000 atm. An equation describing the slope depends on the latent heat of freezing and the molar volume difference between liquid water and ice. Results indicate that negative pressures of −500 atm, which correspond to nanometer-scale water surface curvatures, lead to a roughly 4 K increase in heterogeneous-freezing temperatures. In mixed-phase clouds, this would result in an increase of approximately 1 order of magnitude in active INP concentrations. The findings presented here indicate that any process leading to negative pressure in supercooled water may play a role in ice formation, consistent with experimental evidence of enhanced ice nucleation due to surface geometry or mechanical agitation of water droplets. This points towards the potential for dynamic processes such as contact nucleation and droplet collision or breakup to increase ice nucleation rates through pressure perturbations.

Occurrence and Diversity of Yeast Associated with Fruits and Leaves of Two Native Plants from Brazilian Neotropical Savanna

Background: This work studied the occurrence, density, and diversity of yeast species associated with the leaves and fruits of Sabicea brasiliensis and Anacardium humile. Methods: Fragments of leaves and fruits were subjected to maceration and placed under agitation in peptone water. One hundred µL aliquots of each of the decimal dilutions were plated on YM chloramphenicol agar medium. The different morphotypes were identified through sequence analysis of the 26S rDNA. Results: A total of 83 yeast isolates were recovered from the organs sampled, 40 from fruits and 19 from the leaves of S. brasiliensis, while 14 were recovered from fruits and 10 from the leaves of A. humile. The isolates were identified as belonging to two phyla, six classes, eight orders, and eight families. Most isolates, at 71 (84.3%), belong to Ascomycota, with Saccharomycetes dominant in fruits and Dothideomycetes in leaves. The remaining 12 (15.7%) isolates belong to the phylum Basidiomycota. The most frequent genera were Aureobasidium, Candida, Rhodotorula, and Wickerhamiella. The Wickerhamiella isolates made possible the subsequent description of a new species within this genus. Conclusions: Our data reveal the yeast species that inhabit different Cerrado plant organs and indicate that these hosts can be considered an important habitat for yeast diversity, including new and/or previously unreported species in this biome.

Microporous exposure on catalytic performance of MoVNbTeOx mixed metal oxides in the oxidative dehydrogenation of ethane

The catalytic performance of the non-purified MoVNbTeOx catalyst was optimized by changing the composition of the synthesis gel method in the hydrothermal synthesis process. However, the enhancement in activity was more pronounced for the post-treatment process of the non-purified catalyst. The catalytic performance of non-purified MoVNbTeOx catalysts and phase-pure M1 catalysts in the oxidative dehydrogenation of ethane (ODHE) were enhanced by water agitation post-treatment. The results showed that the phase-pure M1 catalyst obtained by treating the MoVNbTeOx catalyst with nitric acid had an increased activity per unit mass, but with a mass loss of catalyst materials during the purification process. After several days of post-treatment with water agitation, the catalytic activity of the non-purified MoVNbTeOx and the M1 samples gradually increased and stabilized, where both catalysts had a comparable catalytic performance. All the samples were systematically characterized, showing that the catalytic performance of the samples was mainly correlated with the enhanced specific surface area/pore volume. The results show that for the hydrothermally synthesized MoVNbTeOx catalysts, the reaction takes place in the micropores and the key to improve the performance of MoVNbTeOx catalysts is to effectively expose the active sites. Physical post-treatment process that does not require nitric acid or hydrogen peroxide for purification is also effective in enhancing catalyst activity by boosting the active site.

Effects of currents and waves on the morphologies of coastal sandy clinoforms: sediment mobility calculations based on current meter and wave data from Southern California, U.S.A.

ABSTRACT In some wave-exposed coasts, sandy clinoforms occur with rollovers (locations where their surfaces steepen) at ∼ 20–60 m depth. They have been suggested to have formed from sand mobilized by strong wave agitation in shallow water that has deposited in more tranquil deeper water beyond the rollover, although other suggested origins of clinoforms might also apply. In situ information on active sediment transport is needed to address their origins. Here, we assess sediment transport across a sandy clinoform rollover at 25–30 m depth using legacy data from current meters installed across the Southern California shelf near Del Mar in depths of 15, 30, and 60 m. Although lasting only 25 hours, the data captured conditions during the passage of a cyclone, which occurs frequently along this coast. Information from a global meteorological model reveals that waves were 1–2 m in height during the cyclone passage. Using the mean particle size from vibracores (0.129 mm), sand at the 15-m-depth site would have been continuously agitated above its threshold of motion during the 25-hour period, whereas sand at the 30-m site was mobile over 17 hours. Total-load fluxes of sand estimated from the waves and currents were strong at the 15-m site and comprised mostly suspended particles. The cyclone winds drove water, including bottom water, mostly parallel to the coast, but that movement was accompanied by a downwelling component over the first ∼ 10 hours. That downwelling likely moved suspended particles from the topset of the clinoform onto the foreset. A later upwelling component may have partially reversed that particle movement but was unlikely to have been so effective. The results suggest how wave effects, coupled with downwelling currents, dominated the sand transport and deposition over this short 25-hour period, contributing to the clinoform morphology.

Effects of water movement and temperature on Rhizophydium infection of Planktothrix in a shallow hypereutrophic lake.

Grand Lake St. Marys (GLSM) is a popular recreational lake located in western Ohio, United States, generating nearly $150 million in annual revenue. However, recurring algal blooms dominated by Planktothrix agardhii, which can produce harmful microcystin toxins, have raised concerns about water safety and negatively impacted the local economy. Planktothrix agardhii is host to a number of parasites and pathogens, including an obligate fungal parasite in the Chytridiomycota (chytrids). In this study, we investigated the potential of these chytrid (Rhizophydium sp.) to infect P. agardhii blooms in the environment by modifying certain environmental conditions thought to limit infection prevalence in the wild. With a focus on temperature and water mixing, mesocosms were designed to either increase or decrease water flow compared to the control (water outside the mesocosm). In the control and water circulation mesocosms, infections were found infrequently and were found on less than 0.75% of the Planktothrix population. On the other hand, by decreasing the water flow to stagnation, chytrid infections were more frequent (found in nearly 3x as many samples) and more prevalent, reaching a maximum infection rate of 4.12%. In addition, qPCR coupled with 16S-18S sequencing was utilized to confirm the genetic presence of both host and parasite, as well as to better understand the effect of water circulation on the community composition. Statistical analysis of the data confirmed that chytrid infection was dependent on water temperature, with infections predominantly occurring between 19°C and 23°C. Additionally, water turbulence can significantly reduce the infectivity of chytrids, as infections were mostly found in stagnant mesocosms. Further, decreasing the water circulation promoted the growth of the cyanobacterial population, while increasing water agitation promoted the growth of green algae (Chlorophyta). This study starts to explore the environmental factors that affect chytrid pathogenesis which can provide valuable insights into controlling measures to reduce the prevalence of harmful algal blooms and improve water quality in GLSM and similarly affected waterbodies.

Understanding plasticiser leaching from polystyrene microplastics.

Plastic pollution in our oceans is of growing concern particularly due to the presence of toxic additives, such as plasticisers. Therefore, this work aims to develop a comprehensive understanding of the leaching properties of plasticisers from microplastics. This work investigates the leaching of phthalate acid ester (dioctyl terephthalate (DEHT) and diethylhexyl phthalate (DEHP)) and diphenol (bisphenol A (BPA) and bisphenol S (BPS)) plasticisers from polystyrene (PS) microplastics (mean diameter = 136 μm to 1.4 mm) under controlled aqueous conditions (temperature, agitation, pH and salinity). The leaching behaviours of plasticised polymers were quantified using gel permeation chromatography, high performance liquid chromatography and thermal gravimetric analysis, and the particle's plasticisation characterised using differential scanning calorimetry. Leaching rates of phthalate acid ester and diphenol plasticisers were modelled using a diffusion and boundary layer model, whereby these behaviours varied depending on their plasticisation efficiency of PS, the size of the microplastic particle and the surrounding abiotic conditions. Leaching behaviours of DEHT and DEHP were strongly influenced by the microplastic-surface water boundary layer properties, thus wave action (i.e., water agitation) increased the leaching rate of these plasticiser up to 66 % over 21-days, whereas BPA and BPS plasticisers displayed temperature- and size-dependent leaching and were limited by molecular diffusion throughout the bulk polymer (i.e., the microplastic). This information will improve predictions of plasticiser concentration (both that remain in the plastic and released into the surrounding water) at specific time points during the lifetime of a plastic, ultimately ensuring greater accuracy in the assessment of toxicity responses and environmental water quality.

Maximum recommended and allowable Radon-222 limits in water and air: Systematic review

Radon-222 is a radioactive gas that, when inhaled at high concentrations, can harm human health. However, there are several recommended and maximum allowable Radon-222 limits in water and air in the international community. Thus, this research aimed to evaluate the maximum recommended and allowed Radon-222 limits in drinking water and indoor air in the international community, indicating the most referenced organizations in Radon-222 studies through a systematic review. The results indicate that there is variation of up to 1000% between limits established for Radon concentrations in the air indicated by ICRP and US EPA. For water, the maximum limit established by EURATOM is 90 times higher than that established by US EPA. Greater relevance regarding the presence of Radon-222 in the air was also evidenced, due to its potential to detach from various physical means, such as water agitation, its occurrence in building materials and its release by contaminated soil. Finally, it was also found that the limits imposed by US EPA for the presence of Radon-222 in water and air were the parameters most used for comparison in the scientific community and that about 80% of evaluated studies reported from one two sources that proposed Radon-222 limits in air and water.

Probing maltodextrins surface properties by atomic force microscopy: Interplay of glass transition and reconstitution properties

Reconstitution kinetics of three maltodextrins powders with different dextrose-equivalent (DE) values (low, intermediate, high DE) were evaluated under the glassy and rubbery states. Reconstitution times were found mostly shear rate of agitation in water and DE dependent in the glassy state, with shorter reconstitution times for high shear rates and DE. For powders under the rubbery state, reconstitution times were less shear rate dependent, especially for high DE values. To have a better understanding of powder surface features that can impact reconstitution properties, single particles surface topographies and nanomechanical properties were probed by Atomic Force Microscopy (AFM). It was shown that surface roughness was higher for high DE maltodextrins under the glassy state, whereas a surface smoothing and slight hollows formation was observed for all powders under the rubbery state. Also, a significant reduction and uniformity of Young modulus at the particle surface were observed under the rubbery state. Finally, surface modification at microscale (smoothing and softening) was linked to powder behavior evolution at macroscale (relative shear rate independence during reconstitution) when the powder crosses the glass transition. • Glass transition significantly impacted maltodextrin reconstitution properties. • Surface topographies revealed surface smoothing above glass transition. • Surface nanoscale hollow formation was observed at the rubbery state. • Young modulus decreased significantly at the rubbery state.

Transition Metal Carbo‐Chalcogenide “TMCC:” A New Family of 2D Materials (Adv. Mater. 26/2022)

Transition Metal Carbo-Chalcogenides In article number 2200574, Michael Naguib and co-workers report on the synthesis of 2D transition metal carbo-chalcogenides (TMCCs) by exfoliating their bulk layered counterparts (e.g., Nb2S2C and Ta2S2C) through electrochemical Li-ion intercalation followed by agitation in water. 2D TMCCs combine the surface of 2D TM dichalcogenides (TMDCs) and the core of 2D TM carbides (MXenes) offering unique characteristics of both TMDCs and MXenes.

Environmental parameters modulate lead chloride toxicity on Artemia salina

Introduction: Different environmental conditions can influence the effects of toxic agents on living beings. Recently, a series of experiments performed in Artemia salina submitted to different kinds of intoxication have shown that both, isotherapic and succussed water can change Artemia salina´s bio resilience at different levels. Moreover, it seems to vary according to the circalunar cycle. Objective: To verify if circalunar phases and water agitation can modify the toxicity of lead chloride on Artemia salina in vitro. Methodology: Artemia salina cysts were exposed to seawater containing 0.04% of lead chloride (equal to EC10 or 10% effective concentration, previously determined in a pilot study) in 96-well culture plates. Thirty-six experimental repetitions were performed in four series to observe the possible effects of adding stirred water, the so-called succussed water, and the moon phases. The hatched cysts were recorded after 48 hours using a digital microscope (1000x magnification) to identify the hatching percentage and the viability and mobility of the born nauplii. Results: The exposition of cysts to PbCl2 led to an increase in the hatching rate, and it was more evident during the full moon (p = 0.00014) The addition of succussed water into the seawater medium reduced this effect to the baseline levels. An increase in mobility was seen in nauplii born from exposed cysts during the full moon (p = 0.00077), but this effect was not affected by the treatment with succussed water. Discussion: Although the effects of lead chloride EC10 on the increase of nauplii hatching were expected, two environmental variables changed the sensitivity of cysts to this harmful stimulus. The circalunar cycle varied the hatching rate according to the moon phase, even in laboratory conditions, and the addition of succussed water into the medium reduced the hatching rate, even with different intensities according to the moon phase. The organization of nano and microbubbles generated after the succussion of water could be related to this protective effect and can explain, at least partially the effects of high diluted preparations on this biological context. Conclusion: Environmental factors, such as the circalunar cycle and products of water agitation, can modulate the adaptative control of hatching in Artemia salina exposed to lead chloride at EC10.

REUSE OF THE AQUEOUS PHASE OF BIO-OIL FRACTIONATION AS A WATER-REPELLENT AGENT FOR WOOD

A simple method to extract pyrolytic lignin from bio-oil is under agitation in water or organic solvent. This process produces a water-insoluble fraction (pyrolytic lignin) and a water-soluble fraction (WS). In this study, we used a physical fractionation technique with water as a liquid agent to separate the two fractions of the fast pyrolysis bio-oil and obtain the WS — the object of study — to test its efficiency as a protective agent for lignocellulosic materials. The study aimed to investigate the efficiency of the aqueous phase (WS) as a water-repellent agent when impregnated into Pinus elliotti wood. To obtain WS, we used two bio-oil:water ratios (1:50 and 1:100) and two agitation speeds (17,000 and 8,500 RPM); they were respectively named WS50 and WS100, both with an average yield of 61% WS. Gas chromatography coupled with mass spectrometry (GC-MS), thermogravimetry (TGA), contact angle, and scanning electron microscopy (SEM) were used to characterize the WS and the veneers impregnated with it. There were no morphological changes on their surface, especially regarding the non-coating of the wood pits; meanwhile, the TGA showed visible changes in the degree of thermal degradation of the impregnated material related to the chemical composition of the WS identified in the GC-MS. There was a significant increase, on average 62%, in the apparent contact angle of the impregnated wood, approximately 126°. The WS has shown to be efficient as a protective agent by converting the hydrophilic surface of Pinus elliotti into a hydrophobic one, and this effect partially remained after 45 days of exposure.

Development and evaluation of a point-of-use UV appliance for fresh produce decontamination

In-house treatment strategy for fresh produce decontamination has not been emphasized as much as industrial washing. The most common treatment for fresh produce decontamination and cleaning at home and other point-of-use places such as cafeteria is rinsing and/or soaking in a sink. In this study, an appliance utilizing UV and agitated water to decontaminate fresh produce was developed and its effectiveness was investigated in an aim to identify optimum processing parameters. Grape tomato and spinach representing two different surface smoothness were dip-inoculated in a four-strain Salmonella cocktail to reach a final population of 5–8 log CFU/g and air-dried. The produce samples were then washed in 1 gallon tap water under varying conditions, water agitation speed (0–190 RPM), sample size (50–400 g), UV intensity (0–30 mW/cm2) and treatment time (2, 5 and 10 min). In general, increasing the agitation speed and UV intensity enhanced Salmonella inactivation for both grape tomato and spinach. Sample size significantly affected the UV inactivation of Salmonella on grape tomato, but not on spinach. The effect of extending treatment time from 2 to 10 min was insignificant for almost all the UV treatments and the controls. The effect of UV intensity and treatment time on inactivation of Salmonella on spot-inoculated grape tomato and spinach was also determined. The most severe treatment used in this study, 30 mW/cm2 UV for 10 min, resulted in >4 log reductions of Salmonella dip- or spot-inoculated on grape tomato (200 g sample size and 190 RPM agitation speed) and 3.5 log reductions of Salmonella dip- or spot-inoculated on spinach (100 g sample size and 110 RPM agitation speed). We foresee that the UV appliance developed and evaluated in this study could be further fine-tuned and optimized to eventually construct a point-of-use UV appliance that can be used at home, cafeteria, restaurants, and hospitals for fresh produce decontamination and cleaning. The UV appliance could be an inexpensive and effective tool to improve fresh produce safety.

The Effect of Ultrasonic Cleaning Upon Mechanical Properties of Metal Matrix Composites

The aim of this study is to produce composite materials by recycling metallic chips, which are found in industry as a large amount of waste. In addition, it is aimed to investigate the effect of ultrasonic cleaning process as the consolidation behavior and mechanical properties of bulk material directly depend on the cleaning of waste metallic chips. In the present investigation, spheroidal graphite cast iron (GGG-40) was employed as reinforcement material in tin bronze (CuSn10) matrix system. GGG-40 and CuSn10 chips were cleaned by ultrasonic agitation in water for 20 and 40 min. Consolidation of the cleaned metallic chips was achieved with a hot press by applying 820 MPa pressure under 450 °C, and the cylindrical and prismatic metal matrix composite materials with different reinforcement ratios were successfully produced. Energy-dispersive X-ray and scanning electron microscopy analyses were carried out to determine the amount of the oxide removed from the surfaces of chips. The mechanical properties of the samples were determined by hardness, porosity, compression and three-point bending tests. According to the results of the analyses, it was found that CuSn10 surfaces were cleaned from 20%, 50% and GGG-40 surfaces from 35%, 39% oxides during 20- and 40-min cleaning time, respectively. In addition, the results of the mechanical tests revealed that increased ultrasonic cleaning time improves the consolidation quality of metallic chips and it provides successful covering of GGG-40 chips by the CuSn10 chips as a result of a better structural integrity. New machinery parts with high mechanical properties can be produced as a result of recycling of the metallic chips which are available as waste in industry by appropriate cleaning process and this situation makes this study more innovative, economical and environmentally friendly research.

The effect of SDS surfactant on surface reaeration coefficient: a laboratory scale approach

Surface reaeration coefficient (K2), which represents the transfer of oxygen at the air-water interface, is an important variable in aquatic ecosystems. K2 is influenced by several factors, including surfactants; furthermore, this coefficient is used in water-quality models, which requires its correct estimation. This study evaluated the effects of the surfactant Sodium Dodecyl Sulfate (SDS) on K2 in two different experimental systems. In a cylindrical reactor with a turbine-type mechanical stirrer, 15 reaeration experiments were carried out with SDS concentrations of 0.0; 0.25; 0.5; 1.0 and 1.5 mMol L-1 and stirrer rotation velocities of 25, 50 and 100 rpm. In a circular hydraulic channel, 8 reaeration experiments were carried out, in triplicate, with SDS concentrations of 0 and 1.5 mMol L-1 and agitation levels of Reynolds 4,500, 37,500; 49,200 and 54,000. In the reactor, regardless of the rotation velocity, the surfactant reduced K2 by 20%, due to a superficial film formation at the interface that made oxygen transfer difficult, due to a phenomenon known as “barrier effect”. In the channel, an approximate K2 reduction of 15% occurred at higher levels of water agitation. In the presence of surfactants, and at low levels of agitation, phenomena that increase K2 (i.e., Marangoni effect) may coexist with those that reduce K2 (i.e., barrier effect). We concluded that the presence of SDS in aquatic environments should be considered when estimating the surface reaeration coefficient, because this surfactant can contribute to uncertain K2 estimation.