Comparative Study of the Effect of Solvents on the Efficacy of Neonicotinoid Insecticides Against Malaria Vector Populations Across Africa

Background New insecticides with a novel mode of action such as neonicotinoids have recently been recommended for public health by WHO. Resistance monitoring of such novel insecticides requires a robust protocol to monitor the development of resistance in natural populations. In this study, we comparatively used three different solvents to assess the susceptibility of malaria vectors to neonicotinoids across Africa.MethodsMosquitoes were collected from May to July 2021 from three agricultural settings in Cameroon (Njombe-Penja, Nkolondom, and Mangoum), the Democratic Republic of Congo (Ndjili-Brasserie), Ghana (Obuasi), and Uganda (Mayuge). Using the CDC bottle test, we compared the effect of three different solvents (ethanol, acetone, MERO) on the efficacy of neonicotinoids against Anopheles gambiae s.l. In addition, TaqMan assays were used to genotype key pyrethroid-resistant markers in An. gambiae and to evaluate potential cross-resistance between pyrethroids and clothianidin.ResultsLower mortality were observed when using absolute ethanol or acetone alone as solvent (11.4- 51.9% mortality in Nkolondom, 31.7- 48.2% in Mangoum, 34.6- 56.1% in Mayµge, 39.4- 45.6% in Obuasi, 83.7- 89.3% in Congo and 71.05- 95.9% in Njombe pendja) compared to acetone + MERO for which 100% mortality were observed for all the populations. Synergist assays (PBO, DEM and DEF) revealed a significant increase of mortality suggesting that metabolic resistance mechanisms are contributing to the reduced susceptibility. A negative association was observed between the L1014F-kdr mutation and clothianidin resistance with a greater frequency of homozygote resistant mosquitoes among the dead than among survivors (OR=0.5; P=0.02). However, the I114T-GSTe2 was in contrast significantly associated with a greater ability to survive clothianidin with a higher frequency of homozygote resistant among survivors than other genotypes (OR=2.10; P=0.013). ConclusionsThis study revealed a contrasted susceptibility pattern depending on the solvents with ethanol/acetone resulting to lower mortality, thus possibly overestimating resistance, whereas the MERO consistently showed a greater efficacy of neonicotinoids but it could prevent to detect early resistance development. Therefore, we recommend monitoring the susceptibility using both acetone alone and acetone+MERO (8-10µg/ml for clothianidin) to capture the accurate resistance profile of the mosquito populations.

Comparative Study of the Effect of Solvents on the Efficacy of Neonicotinoid Insecticides Against Malaria Vector Populations Across Africa

Background: New insecticides with novel modes of action such as neonicotinoids have recently been recommended for public health use by WHO. Resistance monitoring of such novel insecticides requires a robust protocol to monitor the development of resistance in natural populations. In this study, we comparatively used three different solvents to assess the susceptibility of malaria vectors to neonicotinoids across Africa.Methods: Mosquitoes were collected from May to July 2021 from three agricultural settings in Cameroon (Njombe-Penja, Nkolondom, and Mangoum), the Democratic Republic of Congo (Ndjili-Brasserie), Ghana (Atatam), and Uganda (Mayuge). Using the CDC bottle test, we compared the effect of three different solvents (ethanol, acetone, acetone+MERO) on the efficacy of neonicotinoids against Anopheles gambiae s.l. In addition, TaqMan assays were used to genotype key pyrethroid-resistant markers in An. gambiae and to evaluate potential cross-resistance between pyrethroids and clothianidin.Results: Lower mortalities were observed for all populations when using absolute ethanol or acetone alone as solvent (11.4- 51.9% mortality for Nkolondom, 31.7- 48.2% for Mangoum, 34.6- 56.1% for Mayuge, 39.4- 45.6% for Atatam, 83.7- 89.3% for Congo and 71.05- 95.9% for Njombe pendja) compared to acetone + MERO for which 100% mortality was observed for all the populations. Synergist assays (PBO, DEM and DEF) revealed a significant increase of mortality suggesting that metabolic resistance mechanisms are contributing to the reduced susceptibility. A negative association was observed between the L1014F-kdr mutation and clothianidin resistance with a greater frequency of homozygote resistant mosquitoes among the dead than among survivors (OR=0.5; P=0.02). However, the I114T-GSTe2 was in contrast significantly associated with a greater ability to survive clothianidin with a higher frequency of homozygote resistant among survivors than other genotypes (OR=2.10; P=0.013). Conclusions: This study revealed a contrasted susceptibility pattern depending on the solvents with ethanol/acetone resulting in lower mortality, thus possibly overestimating resistance, whereas the addition of MERO consistently increased the efficacy of neonicotinoids in terms of percentage mortalities and time to final mortality. The addition of MERO could however prevent the early detection of resistance development. We therefore recommend monitoring susceptibility using both acetone alone and acetone+MERO (8-10µg/ml for clothianidin) to capture the accurate resistance profile of the mosquito populations.

How Does EOR Polymer Impact Scale Control During ASP Flooding?

Polymer based enhanced oil recovery (EOR) technology has drawn more and more attention in the oil and gas industry. The impacts of EOR polymer on scale formation and control are not well known yet. This research investigated the impacts of EOR polymer on calcite scale formation with and without the presence of scale inhibitors. Seven different types of scale inhibitors were tested, including four different phosphonate inhibitors and three different polymeric inhibitors. Test brines included severe and moderate calcite scaling brines. The severe calcite brine is to simulate alkaline surfactant polymer (ASP) flooding conditions with high pH and high carbonate concentration. The test method used was the 24 hours static bottle test. Visual observation and the residual calcium (Ca2+) concentration determination were conducted after bottle test finished. It was found that EOR polymer can serve as a scale inhibitor in moderate calcite scaling brines, although the required dosage was significantly higher than common scale inhibitors. Strong synergistic effects were observed between EOR polymer and phosphonate scale inhibitors on calcite control, which can significantly reduce scale inhibitor dosage and provides a solution for calcite control in ASP flooding. The impact of EOR polymer on polymeric scale inhibitors varied depending on polymer types. Antagonism was observed between EOR polymer and sulfonated copolymer inhibitor, while there was weak synergism between EOR polymer and acrylic copolymer inhibitors. Therefore, when selecting scale inhibitors for polymer flooding wells in the future, the impact of EOR polymer on scale inhibitor performance should be considered.

Design of industrial wastewater demulsifier by HLD-NAC model

The chemical method is one of the treatment techniques for the separation of oil–water emulsion systems. The selection of appropriate demulsifiers for each emulsion system is the most challenging issue. Hydrophilic-lipophilic-deviation (HLD) is a powerful semi-empirical model, providing predictive tools to formulate the emulsion and microemulsion systems. This work aims to apply HLD to obtain an optimal condition for demulsification of oil-in-water emulsion system—real industrial wastewater—with different water in oil ratios (WOR). Therefore, the oil parameter of the contaminant oil and surfactant parameter for three types of commercial surfactants were calculated by performing salinity scans. Furthermore, the net-average-curvature (NAC) framework coupled with HLD was used to predict the phase behavior of the synthetic microemulsion systems, incorporating solubilization properties, the shape of droplets, and quality of optimum formulation. The geometrical sizes of non-spherical droplets (Ld, Rd)—as an indicator of how droplet sizes are changing with HLD—were consistent with the separation results. Correlating Ld/Rd at phase transition points with bottle test results validates the hypothesis that NAC-predicted geometries and demulsification behavior are interconnected. Finally, the effect of sec-butanol was examined on both synthetic and real systems, providing reliable insights in terms of the effect of alcohol for WOR ≠ 1.

Affinity between Bitumen and Aggregate in Hot Mix Asphalt by Hyperspectral Imaging and Digital Picture Analysis

This study investigated the viability of quantifying the affinity between aggregate and bitumen by means of different imaging techniques. Experiments were arranged in accordance with the rolling-bottle test, as indicated in UNI EN 12697-11, “Test methods for hot bituminous conglomerates—Part 11”. Digital image processing (DIP) techniques have only recently been used for such quantification. The data gathered with a multi-sensor optical platform equipped with VIS–NIR and SWIR spectrometers were compared with DIP outcomes. Data were processed using the unsupervised ISODATA and the supervised parallelepiped algorithms. The exposed aggregate index (EAI) and the bitumen index (BIT) were calculated to retrieve the bitumen percentage coverage of different mixtures. The comparison with the results obtained employing the traditional 6, 24, 48 and 72 testing hours reveals the possibility to implement a standardized analysis methodology combining digital and hyperspectral imagery to highlight potential inaccuracies deriving from the visual interpretation.

Адгезійні властивості бітуму, модифікованого епоксидом рослинного походження у присутності ініціаторів

Модифікація бітумних в'яжучих епоксидними сполуками є ефективною технологією для зміни якісних властивостей дорожніх бітумів, яка дає змогу отримувати якісні, довговічні дорожні конструкції. Проте фізико-механічні властивості модифікувальних епоксидних систем недостатньо вивчено. Проте використання нафтової сировини для виробництва епоксидних смол є досить дороговартісним і не екологічним. Тому в цій роботі запропоновано використовувати для приготування епоксидасфальтів епоксидні сполуки на підставі рослинного походження, зокрема ріпакової олії, для модифікації дорожніх бітумів. Такі епоксиди досить дешеві у виробництві, доступні, екологічні і виготовляють їх з поновлюваної сировини, яку в достатній кількості продукує Україна. Нам вдалося підвищити якісні властивості дорожнього бітуму за допомогою модифікації дорожнього бітуму епоксидом ріпакової олії. Досліджено вплив модифікатора епоксиду ріпакової олії (BERO) на фізико-механічні властивості модифікованого бітуму різними способами для підтвердження позитивного впливу добавки на зчеплювальні властивості бітуму. Вивчено адгезійні властивості модифікованого бітуму до скла та каменю, а також схильність бітумів до відшарування від щебеню впродовж тривалого періоду часу (rolling bottle test). Досліджено ефективність BERО після прогрівання бітуму. Також вивчено зчеплювальні властивості бітуму, модифікованого BERО, залежно від типу затверджувача: адипінової кислоти (АА), малеїнового ангідриду (МА) та поліетиленполіаміну (PEPA). Кращі зчеплювальні властивості з мінеральними матеріалами показав бітум, модифікований композицією BERO+PEPA. Композиції BERO+АА та BERO+МА показали практично однакові результати. Під час досліджень встановлено, що використання АА, МА чи PEPA як ініціатора дає змогу покращувати технологічні парметри процесу модифікування нафтових бітумів. Адгезійні властивості модифікованого бітуму було підтверджено різними сучасними методами аналізу.

Nanoscale Silica Coated Graphene Oxide and Its Demulsifying Performance in Water-in-oil and Oil-in-water Emulsions

In present study, GO@SiO2 nanocomposites was prepared by coating nanoscale silica onto graphene oxide (GO). The nanocomposites were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (IF-IR). Additionally, the demulsifying performance of the nanocomposites was investigated by the bottle test method. The results showed that GO@SiO2 nanocomposites had a good demulsifying performance both in oil-in-water (O/W) and water-in-oil (W/O) emulsions. When the concentration of GO@SiO2 was 200 ppm in O/W emulsion, the optimal light transmittance of aqueous phase (LTA) and corresponding oil removal rate (ORR) at room temperature could reach 86.9% and 99.48%, respectively. Also, GO@SiO2 had an excellent salt tolerance under acidic condition. Furthermore, GO@SiO2 nanocomposites also could demulsify the W/O emulsion, and the efficiency at 70℃ could reach 80.5% when the concentration was 400 ppm.

Emulsion Characterization of the Heavy Oil-Alkaline Water System in Alkaline Flooding Mechanism Investigation Using a Combination of Modified Bottle Test and Sandpack Flooding

Due to the diversity of alkali categories and reservoir conditions, the varied oil recovery driving mechanism of alkaline flooding is subjected to different types of emulsion generation. In this study, a modified bottle test method that assesses major emulsion type formation for preliminary prediction of alkaline flooding performance in oil recovery is introduced. The modified method considers the necessary energy input required for mixing immiscible bulk phases at low interfacial tension (IFT) regions to improve the representativity of emulsion formation in the bottle test to that of in porous media. To accurately evaluate the emulsion type and phase volume distribution from the bottle test, each emulsion phase after aging in the test bottle was sampled and its water content was measured through Karl Fischer titration. Afterward, material balance calculations other than pure volume observation were applied to quantify the emulsion volume and determine the major emulsion type formation. It is found that the majority of emulsion effluent type from the sandpack flooding test were in agreement with the bottle test forecast which proved the feasibility of the modified bottle test method. The statistically optimized experimental designs were implemented due to the simplicity of the new bottle test method and it considerably cut the time expense regarding the alkaline flooding performance prediction. The high versatility of the modified bottle test ensures that the alkali usage is not limited to the inorganic alkalis mentioned in this study; other type of alkaline solutions can also be used for further expanding the scope of its application.

A new method to select demulsifiers and optimize dosage at wet crude oil separation facilities

The current practice for crude oil demulsifier selection consists of pre-screening of the best performing demulsifiers followed by field trials to determine the optimum demulsifier dosage. The method of choice for demulsifier ranking is the bottle test. As there is no standard bottle test method, there are different methodologies reported in the literature. In this work, a new approach to bottle test and field trial was described which improved significantly the selection and dosage of the demulsifier. The bottle test was optimized by measuring an accurate mass of demulsifier. This method produces repeatable results. This bottle-test methodology was benchmarked against field trial results performed in oil processing plants. The field trials were also improved to avoid the accumulation effect of demulsifier, when optimizing their dosage. The field data for the optimization of demulsifier dosage was analyzed mathematically; and a graphical method to determine the optimum range is described.

Optimization of (RP6000 and MAKS-9150) demulsifiers for separation of water from (Kirkuk / baba, Khbbaz) crude oil emulsion

In this study oil-soluble (RP6000 and MAKS-9150) emulsion breakers have been selected for separation of water from Kirkuk / baba (50oC), Khbbaz (40oC) crude oil emulsions and their activity measured using the Bottle test method at different concentration and found the activity of RP6000 demulsified best than MAKS-9150 emulsion breakers. RP6000 separated water (100%) in (15)min., (40)ppm and in (60)min., (20)ppm of demulsified for Kirkuk/ baba Crude oil and for khbbaz Crude oil the (100%) water separation was in (15)min., (80)ppm and in (30)min., (60)ppm and PH effect, salinity, temperature and density of emulsion stability depending on literature were explained for Optimization.