Aquatain® Causes Anti-Oviposition, Egg Retention, Oocyte Melanization and Triggers Female Death in Ae. Aegypti

Background: In arboviral disease systems where the virus can be transmitted from male to female and from one generation to the next, targeting the female (especially when she is pregnant) can help alter the persistence of the virus in nature and its transmission. This is typical of Ae. aegypti, which has been unmanageable due to the development of insecticide resistance. Despite evidence that monomolecular surface films prevent the selection of genetic resistance, their potential in Aedes vector control remains largely unexplored. Methods: We examined the oviposition, egg retention, oocyte melanization, and female mortality of the Cayman Islands strain of Ae. aegypti, using choice and no-choice bioassays involving Aquatain® Mosquito Formulation (AMF). Results: When presented with similar opportunities to oviposit in two sites treated with AMF and two others with water (control), egg deposition rates were significantly higher in water than in oil presence. We also observed a matching pattern of egg deposition preference in arenas with more options in AMF-treated sites. Females laid appreciably more eggs when water was the only available medium than when all sites were treated with AMF. Also, considerably more mature eggs were withheld in the AMF no-choice arena than in the no-choice test involving only water. Internal oocyte melanization was not observed in females from the oviposition arenas with the lowest oil presence (equal-choice and water-based no-choice); in contrast, this physiological response intensified as the number of AMF-treated sites increased. Female death occurred at high rates in AMF-treated environments, and this response increased with the increasing presence of such egg deposition sites. Conclusions: This study demonstrated that AMF acted as a deterrent signal to ovipositing Ae. aegypti and an indirect adulticide. Referring to its previously reported direct toxicity on the aquatic stages of this mosquito and its biodegradability, AMF should be incorporated as a critical component in integrated control strategies for dengue and related diseases.

Investigation of Zohr Hydraulic Flying Lead Reaction Drive Shafts

The HFLs for the Zohr Phase 1 project contains a cobra head at each end that incorporates the female couplers and the locking mechanism. Beginning in February 2020, and with the most recent incident recorded in September 2020, a total of 4 supplied HFL reaction drive shafts (RDS) failed subsea, resulting in partial separation of the HFL cobra heads from their respective fixed stabplates with a loss of hydraulic supply pressure and subsequent automatic well shut ins. HFL failures occurred on both the XT and HIPPS side of the HFLs on 3 different well sites. A further RDS tested at the laboratory from the UTA end of an HFL showed signs of microscopic cracking consistent with the failed specimens suggesting it may have had the potential to lead to a failure in the future. The failed HFLs were retrieved and returned onshore, the HFL locking mechanism was stripped down to gain access to the failed ends of the RDS and a visual inspection was performed. The initial inspection after partial disassembly to reveal the inside of the HFL locking mechanism identified that the RDS had completely failed at a location on the threaded portion of the RDS. Surface deposits were collected from each probe surfaces and analysed using scanning electron microscopy (SEM), together with energy- dispersive X-ray (EDX). A piece 10mm long was taken from each of the four probes for quantitative chemical analysis. Standard tensile and Charpy V-notch impact and Vickers hardness surveys have been conducted. Each of the failed probe exhibited an intergranular fracture surface morphology. This was confirmed through metallography/EBSD. No single initiation site was located on fracture surfaces, although some regions showed a mixed fractographic morphology, with some small areas of micro-void coalescence. Secondary intergranular cracking and corrosion was apparent at various locations, in each of the failed probes, including in thread roots, in samples 183 and 188, and just above the thread, in sample 052. These observations points towards an environmentally assisted cracking mechanism (i.e. stress corrosion cracking). Metallography revealed two layers within surface films, both in cracks and on the fracture surface: an inner layer, rich in nickel, sulphur and aluminium, and an outer, rich in copper and sulphur. Mechanical testing and chemical analysis revealed consistent results across the probes. The probe material was specified as Nibron Special (CuNi14Al3/DIN 2.1504) with a size of 2inch. Would be challenging to get the full root cause of using this material for subsea applications as it is resistant to seawater. Another factor contributed allows risk of material failure which should be eliminated for all subsea industry or taken into consideration to avoid further failures.

Influence of aldol condensation processes on the formation of surface films during friction in ester lubricants

The boundary lubrication mode is usually implemented in conditions of low sliding speeds and high loads. The formation of strong boundary lubricating films under this friction mode determines the operability and durability of the friction units. It is believed that the formation of surface boundary films during friction includes the stages of the lubricant oxidation, and the aldol condensation reaction of oxidized molecules. As a result, high-molecular substances called “friction polymers” are formed. The paper studies the formation of surface films in the presence of substances with different reactivity in the aldol condensation and Claisen condensation reactions. Sunflower oil, bis (2-ethylhexyl) sebacate (DEHS), triisodecyl benzene-1,2,4-tricarboxylate (TC) were used as lubricants. It is shown by ATR IR-spectroscopy of that the common thing for the studied oils is that the C=O and C-O groups participate in the formation of boundary films in these oils. The addition of substances, active in aldol condensation reactions, into lubricants does not accelerate the formation of boundary films. Additives that can chemically interact with iron contribute to the dissolution of the surface oxide film and accelerate the formation of boundary layers. The formation of “friction polymers” occurs when the lubricant molecules interact with the metal surface.

Effects of Natural and Artificial Surfactants on Diffusive Boundary Dynamics and Oxygen Exchanges across the Air–Water Interface

Comparing measurements of the natural sea surface microlayer (SML) and artificial surface films made of Triton-X-100 and oleyl alcohol can provide a fundamental understanding of diffusive gas fluxes across the air–water boundary layers less than 1 mm thick. We investigated the impacts of artificial films on the concentration gradients and diffusion of oxygen (O2) across the SML, the thickness of the diffusive boundary layer (DBL), and the surface tension levels of natural seawater and deionized water. Natural and artificial films led to approximately 78 and 81% reductions in O2 concentration across the surfaces of natural seawater and deionized water, respectively. The thicknesses of the DBL were 500 and 350 µm when natural SML was added on filtered and unfiltered natural seawater, respectively, although the DBL on filtered seawater was unstable, as indicated by decreasing thickness over time. Triton-X-100 and oleyl alcohol at a concentration of 2000 µg L−1 in deionized water persistently increased the DBL thickness values by 30 and 26% over a period of 120 min. At the same concentration, Triton-X-100 and oleyl alcohol decreased the surface tension of deionized water from ~72 mN m−1 to 48 and 38 mN m−1, respectively; 47% recovery was recorded after 30 min with Triton-X-100, although low surface tension persisted for 120 min with oleyl alcohol. The critical micelle concentration values of Triton-X-100 ranged between 400 and 459 µg L−1. We, therefore, suggest that Triton-X-100 resembles natural SML because the reduction and partial recovery of the surface tension of deionized water with the surfactant resembles the behavior observed for natural slicks. Temperature and salinity were observed to linearly decrease the surface tension levels of natural seawater, artificial seawater, and deionized water. Although several factors leading to O2 production and consumption in situ are excluded, experiments carried out under laboratory-controlled conditions are useful for visualizing fine-scale processes of O2 transfer from water bodies through the surface microlayer.

Performance Enhancement of Polycrystalline Silicon Solar Cell through Sputter Coated Molybdenum Disulphide Surface Films

The current research focuses on sol-gel derived synthesis and RF sputter deposition of molybdenum disulphide (MoS2) over polycrystalline Si solar cell. Various coating layers were obtained under different sputter deposition at regular intervals. The influence of MoS2 sputter coating on optical, thermal chemical structural properties was examined through various characterisation techniques. 30 minutes coated solar cell reported maximum light transmittance of 95 % in the visible spectrum and minimum electrical resistivity of 2 × 10-3ohm-cm. 30 minutes coated solar cell exhibited maximum power conversion efficiency (PCE) of 19.19 % (open source) and 21.01 % (controlled source). Thermal imaging data reveal that the optimal coating layer experiences a minimum temperature of 33.9 °C and 49.9 °C. From experimental results, sputter deposited MoS2 Si solar cells experience minimum light reflectance and enhanced cell performance.

Surface evolution and corrosion behaviour of Cu-doped carbide-reinforced martensitic steels in a sulfuric acid solution

Cu-doped martensitic steels (Fe–(13, 16)Cr–3W–2Cu–1C) (mass%) with multiple carbide precipitates were prepared at different quenching temperatures, and their corrosion behaviours were examined by measuring the weight loss during immersion in a 0.5 M H2SO4 solution. Lower weight losses and corrosion rates were obtained for the alloy samples prepared at higher quenching temperatures. Surface Cu enrichment was observed for all specimens with a large fraction of dissolved Cr species. Moreover, quenching from higher temperatures not only reduced the amount of M23C6 carbide but also decreased the local electrochemical potential difference between the carbide phase and the martensitic matrix via enhanced surface Cu accumulation, thus increasing corrosion resistance by suppressing microgalvanic corrosion between the constituent phases. The corrosion behaviour of the studied steels was remarkably different from those of the Cu-doped stainless and low-alloy steels with passive oxide surface films, suggesting the strong effect of multiple carbide precipitates on their corrosion behaviour.

Consumption of Entrained Gases Within Bifilms During a Mg-Alloy Casting Process

The formation of entrainment defects, (also known as double oxide film defects or bifilms), caused by the entrapment of a doubled-over surface oxide film containing a small amount of local atmosphere, has been investigated by combining practical experiments using a commercial-purity Mg-alloy under protective gases, with theoretical thermodynamic calculations. Evolution of the entrainment defects was studied, and a double-layered structure of their oxide films was found, which was different from the single-layered structure of the Mg-alloy melt surface films that have been previously reported. A pore gas analyzer was used to analyze the gas trapped within the defects from which H2 and N2 (from the air) were detected. It was found that entrapped gases can be depleted through reactions with the surrounding liquid Mg-alloy, resulting in the oxide films growing together in the melt. Transformation of the entrained gas to solid-phase compounds could reduce the void volume of the defects, thus probably diminishing the negative effect of the entrainment defects on the quality of castings.

Strong Modulation of Short Wind Waves and Ka-Band Radar Return Due to Internal Waves in the Presence of Surface Films. Theory and Experiment

Strong variability of Ka-band radar backscattering from short wind waves on the surface of water covered with surfactant films in the presence of internal waves (IW) was studied in wave tank experiments. It has been demonstrated that modulation of Ka-band radar return due to IW strongly depends on the relationship between the phase velocity of IW and the velocity of drifting surfactant films. An effect of the strong increase in surfactant concentration was revealed in convergent zones, associated with IW orbital velocities in the presence of a “resonance” surface steady current, the velocity of which was close to the IW phase velocity. A phenomenological model of suppression and modulations in the spectrum of small-scale wind waves due to films and IW was elaborated. It has been shown that backscatter modulation could not be explained by the modulation of free (linear) millimeter-scale Bragg waves, but was associated with the modulation of bound (parasitic) capillary ripples generated by longer, cm–dm-scale waves—a “cascade” modulation mechanism. Theoretical analysis based on the developed model was found to be consistent with experiments. Field observations which qualitatively illustrated the effect of strong modulation of Ka-band radar backscatter due to IW in the presence of resonance drift of surfactant films are presented.