Coupled Gas Chromatography Research Articles

Use of lichens as bioindicators of contamination by agrochemicals and metals.

The presence or absence of lichens serves as an indicator of the condition of an ecosystem and the degree to which it is contaminated by various agents, such as agrochemicals and metals. Evaluating the use of lichens as bioindicators of agrochemical contamination could provide a more comprehensive perspective of current contamination levels. Monitoring was conducted over a 4-month period in two study areas: one was a well-conserved area contaminated by metals, and the other was an area surrounded by agricultural crops contaminated by agrochemicals. Data on the presence and abundance of lichens in each study area were recorded at 10 monitoring points, a procedure that was repeated 16 times (every 15days), and concentrations of heavy metals and "organophosphate" agrochemicals in the lichens collected were measured by means of Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES) and Gas Chromatography (GC), respectively. Generalized linear mixed models were used to assess abundance and richness, while general linear mixed models were used to attain Shannon diversity and Simpson dominance indices. Moreover, a multivariate analysis was performed in order to compare the lichen communities in both areas. The results indicated differences between the area contaminated by metals and that contaminated by agrochemicals in terms of abundance and Simpson's dominance index, while no differences were found in the case of the richness and diversity models. The PERMANOVA analysis additionally showed differences between the lichen communities in the two areas. The results also demonstrated that Canoparmelia caroliniana bioaccumulated metals in both areas. The levels of barium, cadmium, and sodium were higher in the area contaminated by metals, while concentrations of chromium and copper were higher in the area contaminated by agrochemicals. Finally, the concentrations of agrochemicals were higher in the area contaminated by agrochemicals and included toxic substances such as Methylparathion and Parathion, which are prohibited in Ecuador. In conclusion, this research underscores the importance of lichens as precise indicators of environmental health and contamination by agrochemicals and metals.

Investigating the emission of volatile organic compound from Cinnamomum camphora

Woodwork has functions as the versatile and sustainable furniture material to decorate buildings in our low-carbon society, while commonly giving significant risks of releasing volatile organic compound (VOC). Thus, how to accurately identify and quantify the VOC of woodwork raw materials is critical. Herein, we designed an easy-to-handle, processable, time-saving strategy of coupling headspace (HS) and gas chromatography (GC) to effectively and precisely investigate the emission behavior of VOC of Cinnamomum camphora (C. camphora). The effects of operation parameters of HS-GC on the VOC emission are analyzed in detail, where the optimize treatment conditions are 140 °C of equilibrium temperature, 25 h of equilibrium time, and 20–40 mesh of particle size. In addition, camphor and eucalyptol are the main chemical components of VOC, which shows the high content, more than 50 % of harvesting VOC. Moreover, a semi-empirical model for VOC emission of C. camphora is established, in which the predicted VOC emission demonstrates a strongly linear relationship with the experimental results (R2 > 0.99). This study enables the comprehensive understanding of VOC emission of raw materials of woodwork, beyond C. camphora, and provides references to effectively reduce VOC in sustainably building and construction.

Mud Volcanoes and Adjacent Vegetation Adaptation in the Rembang Zone, Indonesia: An Approach for Mud Volcano Investigation

Abstract The Rembang Zone is a physiographic zone located in the northern part of Java, Indonesia. Rembang zone includes the areas from Rembang to Tuban and reaches the island of Madura. Ten mud volcanoes were identified, each with varying levels of eruptive intensity. Locals have reported that newly erupted mud materials can disrupt soil fertility in the surrounding areas, leading to vegetation death. Interestingly, we discovered several types of vegetation at mud volcano sites that have adapted, survived, and supported vegetation succession in the surrounding areas. Therefore, in this study, we investigated the vegetation around mud volcanoes in the Rembang Zone and its mud characteristics. We employed Sankey diagram analysis to explore the adapted plant taxa at mud volcano sites in the Rembang Zone. Additionally, we assessed the substrate using Scanning Electron Microscopy (SEM) and conducted geochemical analyses on fluid and non-condensable gas using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Gas Chromatography Mass Spectrometry (GC-MS). The results of this study reveal that there are at least 10 potential mud volcano sites in the Rembang Zone that could be inhabited by vegetation from the Poaceae family (20%), Asteraceae (18%), Cyperaceae (15%), Fabaceae (13%), Euphorbiaceae (9%), and other plant families (2%). These plants tend to adapt to the mud volcano substrate composed of Fe (0.00-0.35 mg/L), Ca (2.9-0.16%), Na (0.02-23.7%), and Cl (13-74%). This demonstrates that vegetation around mud volcanoes in the Rembang Zone can adapt to high-salinity conditions. SEM observations revealed a high smectite content associated with limestone rock. The mud volcanoes frequently emit gases such as N2 (2.3-73%), CH4 (0-8.8%), and CO2 (17-95%), indicating a tendency to produce substrates with nearly water-boiling temperatures (45-105°C). These findings serve as a reference for further understanding the presence of vegetation around mud volcanoes, particularly for identifying the presence of other mud volcanoes through remote sensing.

Attractant and repellent properties of Senna didymobotrya plant extracts to Amblyomma variegatum and Rhipicephalus appendiculatus

The growing challenge of acaricide resistance and geographical range expansion of invasive tick species demands other interventions, like plant-based alternatives, for sustainable tick control. Leaves, flowers, seedpods, and twig branch extracts of Senna didymobotrya were analyzed using coupled gas chromatography mass spectrometry (GC-MS). Response of adult Amblyomma variegatum and Rhipicephalus appendiculatus to extracts was evaluated. The most attractive plant extract was fractionated and ticks’ responses to its fractions assessed. Potential tick attractants in the attractive plant part extract and its fractions were identified by GC-MS analysis. Non- significant qualitative and quantitative differences were observed in the plant parts’ extract composition (R = 0.6178). Flower extracts attracted both species, with a 0.1-fold higher attraction in A. variegatum compared to the standard attraction aggregation attachment pheromone (AAAP). Leaf and seedpod extracts repelled ticks at various concentrations. Bioassays after fractionating flower extracts identified hexane and ethyl acetate fractions as most attractive to A. variegatum (P < 0.001) and R. appendiculatus (P < 0.001), respectively. Chemical analysis of the most attractive extracts and fractions identified compounds, including documented acarine attractants, squalene and linoleic acid. A squalene and linoleic acid blend (1:1) at 1 mg/mL significantly attracted adult A. variegatum (P < 0.01) and R. appendiculatus (P < 0.001). The results of this study broaden comprehension of how ticks respond to plants in nature, and showcase the promising potential for integrating these insights into effective tick management programs.

Pheromonal variation and mating between two mitotypes of fall armyworm (Spodoptera frugiperda) in Africa

In the Americas, the fall armyworm (Spodoptera frugiperda) exists in two genetically distinct strains, the corn (C) and rice (R) strains. Despite their names, these strains are not associated with host plant preferences but have been shown to vary in pheromone composition and male responses. Recently, S. frugiperda was detected in Africa as an invasive species, but knowledge about variation in strain types, pheromone composition and inter-strain mating of populations of the pest in the continent has not been fully examined. Therefore, this study aimed to investigate variations, if any in the pheromone composition of female moths, male moth responses, and mating between C and R mitotypes of S. frugiperda populations in Kenya, as well as their geographic distribution. Strains (mitotypes) of S. frugiperda were identified using mitochondrial DNA (mtDNA) markers, and their pheromonal composition determined by coupled gas chromatography–mass spectrometric (GC–MS) analysis. Male moth responses to these compounds were evaluated using GC-electroantennographic detection (EAD), electroantennogram (EAG), and wind tunnel assays. Oviposition assays were used to determine whether R and C mitotype moths could mate and produce eggs. The results showed that both the R and C mitotypes were present, and there were no statistically significant differences in their distribution across all sampled locations. Five pheromone compounds including (Z)-7-dodecenyl acetate (Z7-12:OAc), (Z)-7-tetradecenyl acetate (Z7-14:OAc), (Z)-9-tetradecenyl acetate (Z9-14:OAc), (Z)-11-tetradecenyl acetate (Z11-14:OAc) and (Z)-11-hexadecenyl acetate (Z11-16:OAc), were detected in the pheromone glands of female moths of both mitotypes, with Z9-14:OAc being the most abundant. The relative percentage composition of Z9-14:OAc was similar in both mitotypes. However, the R mitotype had a 2.7 times higher relative percentage composition of Z7-12:OAc compared to the C mitotype moth, while the C mitotype moth had a 2.4 times higher relative percentage composition of Z11-16:OAc than the R mitotype moth. Male moths of both mitotypes exhibited similar responses to the pheromone compounds, showing the strongest responses to Z9-14:OAc and Z7-12:OAc in electrophysiological and behavioural assays. There was mating between R and C mitotypes with egg production comparable to mating within the same mitotype. Our results revealed that differences between the two S. frugiperda mitotypes are characterized by female moth pheromone composition rather than male moth responses to the pheromones, and that this does not prevent hybridisation between the mitotypes, which may have implications for their management.

Biochemical and functional characterization of milk from alpina and toggenburg goat breeds

Objective: This work aimed to evaluate the biochemical and functional properties of milk from two goat breeds (Alpina and Toggenburg) which could give goat's milk a higher added value and market, making it an attractive option for milk producers.&#x0D; Design/methodology/approach: Several biochemical analyses were performed to both breed milks: Total Fat (Gerber); Total Protein (Lowry); Lactose (reducing sugars); Fatty acid composition (Mass-mass coupled gas chromatography) and antihypertensive activity (angiotensin-converting enzyme inhibition). To determine possible applications, functional characteristics of yogurt and cheese were also evaluated. Statistical analyses were performed using NCSS software.&#x0D; Results: Fat content of Alpina breed was higher than Toggenburg’s (4.76% vs. 2.96%, α=0.00013), as was lactose (8.26% vs. 5.37%, α=0.003), while Toggenburg presented higher protein content (5.53% vs. 4.77%, α=0.00016). Potential biologically active fatty acids were found in both milks in similar concentrations. Toggenburg milk sowed higher antihypertensive activity than Alpina (100% vs 77.27%), which was maintained and in some cases increased, when fermented to obtain different derivatives such as cheese and yogurt.&#x0D; Limitations on study/implications: Further study is still needed to determine the entire biofunctionality of goat’s milk and provide milk producers with options to increase market and added value of their products.&#x0D; Findings/conclusions: Both, Alpina and Toggenburg goat’s milk showed a high Biofunctional potential due to their fat and protein fractions; The fact that biofunctionality can be transferred to derivatives such as yogurt or cheese may increase producers' interest in producing and commercializing it, since the products can be marketed as “functional foods”.

Efficacy of essential oils from three Mentha species against postharvest groundnut pest, Caryedon serratus (Olivier) (Coleoptera: Bruchidae)

Indiscriminate use of chemical pesticides has resulted in many negative implications including degradation of the ecosystem, contamination of food products and effect on non-target organisms. Biopesticides is an efficient and ecofriendly alternative to these synthetic pesticides. Herein, we explored the efficacy of plant-extracted essential oils as a natural alternative to manage groundnut pests. Essential oils extracted from three Mentha species (M. arvensis, M. piperita and M. spicata) were detected for their chemical composition, oviposition deterrence, repellency and electrophysiological responses in groundnut bruchid, Caryedon serratus (Olivier). Gas chromatographic analysis revealed menthol (M. arvensis: 30.43%, M. piperita: 30.18%) and carvone (M. spicata: 65.58%) as the most abundant component in essential oils. Among all the four tested concentrations for the three mentha oils the most significant oviposition deterrence was seen in M. spicata (2% v/w) which completely inhibited oviposition followed by 1.5% M. piperita (21 ± 1.53; p < 0.01), 1.5% M. spicata (28 ± 0.58; p < 0.01) and 1.0% M. arvensis (35 ± 0.58; p < 0.01) oil treated groundnuts after 24 h. M. piperita (86%, ♀) and M. arvensis (70%, ♀) showed promising repellence against the females. In contrast, M. spicata was found to be a potent (90%, ♂) male repellent during olfactometer bioassays. Coupled gas chromatography electroantennogram (GC-EAG) revealed consistent sensory deflections in the antennae of female C. serratus from all the three oils. Our findings revealed promising oviposition deterrence and repellent properties of these mentha oils which offers a prospect in developing effective repellent and its application in integrated pest management, safety of human health, environment and agricultural productivity.

Companion crops alter olfactory responses of the fall armyworm (Spodoptera frugiperda) and its larval endoparasitoid (Cotesia icipe)

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda, is a devastating invasive pest and a threat to food security in Africa, with yield losses of 20–50%. Recent studies highlighted the importance of cereal crops such as maize and sorghum as the most preferred host plants for FAW oviposition. In the current work, we investigated the olfactory responses of FAW and its key larval endoparasitoid Cotesia icipe to odours from the preferred host (maize) in the presence of six potential companion crops including beans, groundnut, sweet potato, greenleaf- and silverleaf desmodium, and cassava. We hypothesized that odours released by companion crops in maize-based intercropping systems would alter host preferences of FAW for oviposition and its parasitoid responses.ResultsIn dual choice oviposition bioassays, FAW laid significantly more eggs on maize than on the other plants. However, in the multiple-choice bioassays, significantly fewer eggs were laid on maize when companion plants were present except cassava. While wind tunnel bioassays confirmed the differential behavioural responses of FAW, we found that its larval endoparasitoid C. icipe was attracted to volatiles from the companion plants tested individually and/or when they were combined with maize. Coupled gas chromatography–mass spectrometry (GC–MS) analysis detected several potential behaviour-modifying compounds including (Z)-3-hexenyl acetate, (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-β-caryophyllene, camphor, methyl salicylate and (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene.ConclusionsOur findings provide evidence supporting diversified maize cropping system could reduce FAW damage by repelling the pest while simultaneously recruiting its natural enemies. Hence, diversifying cereal cropping system with companion crops could serve as an ecologically sustainable FAW management strategy.Graphical

Centaurea triumfetii essential oil chemical composition, comparative analysis, and antimicrobial activity of selected compounds

The essential oils from the Centaurea genus are well known for their pharmacological properties. The most abundant and dominant chemical components in Centaurea essential oils are ß-caryophyllene, hexadecanoic acid, spathulenol, pentacosane, caryophyllene oxide, and phytol. However, whether these dominant components are the key drivers for observed antimicrobial activity remains unclear. Thus, the aim of this study was dual. Here we provide comprehensive, literature-based data to correlate the chemical compounds in Centaurea essential oils with the tested antimicrobial activity. Secondly, we characterized the essential oil of Centaurea triumfettii All. squarrose knapweed using coupled system gas chromatography–mass spectrometry and tested its phytochemicals for antimicrobial activity against E. coli and S. epidermis using disc diffusion assay and monitoring their growth in Muller Hinton broth. The most abundant compounds in C. triumfettii essential oil were hexadecanoic acid (11.1%), spathulenol (10.8%), longifolene (8.8%), germacrene D (8.4%), aromadendrene oxide (6.0%) and linoleic acid (5.3%). Based on our analysis of literature data from other Centaurea essential oils, they were positively correlated with antimicrobial activity. Using an agar disk diffusion method, tested chemical constituents did not show experimental evidence to support this positive correlation to antimicrobial activity when we tested them as pure components. The antibacterial effect of essential oil constituents may be related to a complex synergistic, rather than a single component as suggested by performed network pharmacology analysis, underlying the theoretical interactions between the essential oil phytochemicals listed as potentially responsible for antimicrobial activity and should be confirmed in further in-depth studies. This is the first report on the comparative analysis of Centaurea essential oils with good antimicrobial activity, as well as the first analysis of chemical components of the essential oil from C. triumfettii and the first report of antimicrobial activity of the representative, pure components: aromadendrene, germacrene D, spathulenol, longifolene, and the mixture of selected chemical compounds. This work contributes to the body of knowledge on the genus Centaurea and C. triumfettii species.

Identification of a Female-Produced Sex Attractant Pheromone of the Winter Firefly, Photinus corruscus Linnaeus (Coleoptera: Lampyridae)

Firefly flashes are well-known visual signals used by these insects to find, identify, and choose mates. However, many firefly species have lost the ability to produce light as adults. These “unlighted” species generally lack developed adult light organs, are diurnal rather than nocturnal, and are believed to use volatile pheromones acting over a distance to locate mates. While cuticular hydrocarbons, which may function in mate recognition at close range, have been examined for a handful of the over 2000 extant firefly species, no volatile pheromone has ever been identified. In this study, using coupled gas chromatography - electroantennographic detection, we detected a single female-emitted compound that elicited antennal responses from wild-caught male winter fireflies, Photinus corruscus. The compound was identified as (1S)-exo-3-hydroxycamphor (hydroxycamphor). In field trials at two sites across the species’ eastern North American range, large numbers of male P. corruscus were attracted to synthesized hydroxycamphor, verifying its function as a volatile sex attractant pheromone. Males spent more time in contact with lures treated with synthesized hydroxycamphor than those treated with solvent only in laboratory two-choice assays. Further, using single sensillum recordings, we characterized a pheromone-sensitive odorant receptor neuron in a specific olfactory sensillum on male P. corruscus antennae and demonstrated its sensitivity to hydroxycamphor. Thus, this study has identified the first volatile pheromone and its corresponding sensory neuron for any firefly species, and provides a tool for monitoring P. corruscus populations for conservation and further inquiry into the chemical and cellular bases for sexual communication among fireflies.

Olfactory Stimulants for Sirex nigricornis (Hymenoptera: Siricidae) and its Parasitoid, Ibalia leucospoides (Hymenoptera: Ibaliidae), in Odors of Stressed and Bark Beetle–Colonized Pines

Abstract We conducted studies with the native woodwasp Sirex nigricornis F. (Hymenoptera: Siricidae) in Louisiana to identify host-associated olfactory stimulants that may include attractive semiochemicals for this species as well as Sirex noctilio F., an invasive species that can attack healthy trees. Loblolly pines (Pinus taeda L.) treated with a stressing agent were felled and chipped 1–2 mo after treatment, and the chips were steam–water distilled in a Clevenger apparatus to extract volatile compounds. Using coupled gas chromatography–electroantennographic detection, we analyzed the distillates with antennae of both S. nigricornis and the Sirex parasitoid Ibalia leucospoides (Hochenwarth) (Hymenoptera: Ibaliidae) to identify olfactory stimulants. In addition, we assayed S. nigricornis antennae with synthetic mixtures containing 23 volatile compounds associated with stressed and dying pines, including pheromones of bark beetles (Coleoptera: Curculionidae: Scolytinae) that also use these hosts. Antennae of both male and female S. nigricornis responded to 29 identifiable volatiles in the distillates, whereas I. leucospoides responded to 23 volatiles. Eighteen compounds in the synthetic mixtures were olfactory stimulants for S. nigricornis. Olfactory stimulants in the woodchip distillates were predominantly hydrocarbon and oxygenated monoterpenes, and the strongest antennal stimulants among compounds in the synthetic mixtures were oxygenated monoterpenes associated with pine death and early decay (e.g., verbenone, fenchone, and terpinen-4-ol). Bark beetle pheromones (frontalin, endo-brevicomin, ipsenol, and ipsdienol) also stimulated S. nigricornis antennae. The very large number of host-associated olfactory stimulants for S. nigricornis implies that our data may offer limited assistance in targeting individual compounds for investigation as possible attractants and components for a Sirex lure.

Heterologous expression and functional characterization of Drosophila suzukii OR69a transcript variants unveiled response to kairomones and to a candidate pheromone

Drosophila suzukii is a main pest of berries on all continents. Population control relies on insecticides and a current research challenge is to develop alternative strategies. Methods based on behavior-modifying semiochemicals are widely used against other horticultural insects, and the functional characterization of chemoreceptors facilitates the identification of active compounds. Following heterologous expression of single olfactory receptors (ORs) in ab3A olfactory sensory neurons of D. melanogaster, we screened three transcript variants from the OR69a-locus (DsuzOR69aA, DsuzOR69aB, DsuzOR69aC), demonstrating binding to two possible kairomones (3-octanol and R-carvone) and to a possible fly-emitted volatile compound [(Z)-4-nonenal], although with different pharmacological qualities. By coupling Gas Chromatography to SSR (GC-SSR), these ligands enhanced ab3A-spiking at nanogram-aliquots in a complementary fashion among the different OR69a-variants, and we identified another possible kairomone, methyl salicylate, as the most active and specific ligand for the sole DsuzOR69aB. In testing headspaces collected from D. suzukii females and from the fly-associated yeast Hanseniaspora uvarum we did not observe activation from female headspaces but activation from yeast headspaces. In situ hybridization analysis on D. suzukii antennae suggests unique expression of OR69a-subunits in specific neurons, and points toward co-expression within the same neurons. The OR69a-subunits of D. suzukii constitute cation channels, which binding suggests kairomone specificity, even if effects coexist for a complementary binding of (Z)-4-nonenal. Methyl salicylate is the most active ligand and is specific to the sole DsuzOR69aB, inspiring future investigation to validate potentials of this compound for D. suzukii control strategies.

Direct Construction of Peaks from Free Induction Decay Curves for Gas Chromatography-Molecular Rotational Resonance Spectroscopy without Fourier Transforms.

The concept of coupling gas chromatography with molecular rotational resonance spectroscopy (GC-MRR) was introduced in 2020, combining the separation capabilities of GC with the unparalleled specificity of MRR. In this study, we address the challenge of the high data throughput of MRR spectrometers, as GC-MRR spectrometers can generate thousands to millions of data points per second. In the previous GC-MRR studies, a free induction decay (FID) measurement was Fourier transformed to generate each point on the chromatogram. Such extensive calculations limit the performance, sensitivity, and speed of GC-MRR. A direct approach is proposed here to extract peak intensity from FID using the Gram-Schmidt vector orthogonalization method. First, analyte-free FIDs are used to construct a basis set representing the instrument's background noise, and then the remaining FIDs are orthogonalized to this fixed basis set. Each FID yields a single intensity value after Gram-Schmidt orthogonalization. The magnitude of the orthogonalized analyte FID is the signal intensity plotted in the chromatogram. This approach is computationally much faster (up to 10 times) than the conventional Fourier transform algorithm, is at least as sensitive as the FT algorithm, and maintains or improves the chromatographic peak shape. We compare the sensitivity, linearity, and chromatographic peak shapes for the Fourier transform and Gram-Schmidt approaches using both synthetically generated FIDs and instrumental data. This approach would allow the summed peak intensity to be displayed essentially in real-time, following which identified peaks can be further investigated to identify and quantify the species associated with each.

Characterization, spatial distribution, and health risk assessment of polycyclic aromatic hydrocarbons and heavy metals bounded PM2.5 in urban air of Tabriz, Iran

&#x0D; &#x0D; &#x0D; &#x0D; Introduction: Air and its invisible components play an influential part in the existence of living beings. The two factors of urbanization and industrialization of cities increase the concentration of various compounds in the air. This study has been designed to examine seasonal characterization, spatial distribution and health risk assessment of sixteen Polycyclic Aromatic Hydrocarbons (PAHs) and eleven heavy metals bounded PM2.5 at 16 sites in urban air of Tabriz, Iran.&#x0D; Materials and methods: Glass-fiber filters, peripheral pumps and PMI holder were used with a total 3 L/min flow rate for 24 h sampling Particulate Matter less than 2.5 μm (PM2.5) every 4 seasons at 16 sites from 20nd February to 20th December. Proper solvents are consumed for extraction purposes of these Materials. Inductively Coupled Plasma-Optical Emission Spectrometry (ICP- OES) and Gas Chromatography–Mass Spectrometry GC/MS devices used for analyzing purposes and the spatial distribution of PAHs and heavy metals bounded PM2.5 investigated by ArcGIS 10.3. Excess Lifetime Cancer Risk (ELCR) values and carcinogenicity risk were also calculated for children and adults in different exposure pathways.&#x0D; Results: The annual mean concentrations of PM2.5 were 41.17 μg/m3, ∑16 PAHs bounded-PM2.5 were much higher in autumn and winter (217.47 and 178.32 ng/m3) compared to summer and spring (162.61 and 131.89 ng/m3). The annual mean concentrations of heavy metals bounded-PM2.5 were 138.69 ng/m3. Dermal carcinogenicity risk of exposure with PAHs and ELCR values of heavy metals indicated high risk for adults and children in some stations.&#x0D; Conclusion: Considering the topographic location of the region, Industrial areas and the frequent presence of temperature inversion, such comprehensive researches are needed for control policies&#x0D; &#x0D; &#x0D; &#x0D;

Small hive beetle, Aethina tumida (Coleoptera: Nitidulidae): chemical profile of the cuticle and possible chemical mimicry in a honeybee (Apis mellifera) pest

The small hive beetle, Aethina tumida (Coleoptera: Nitidulidae), is an economically important pest of the Western honeybee, Apis mellifera (Hymenoptera: Apidae). We investigated the effect of rearing environment on the cuticular chemical profile of adult A. tumida, using hexane to extract the hydrocarbons and other compounds from the cuticles of beetles. Beetles were collected from A. mellifera colonies in Australia as well as reared in single sex laboratory cultures on different diets. We investigated whether rearing environment (laboratory vs. field, different apiaries, access to mating partners, diet) had any effect on cuticular hydrocarbons. Coupled gas chromatography–mass spectrometry analyses of the extracts showed that rearing environment had significant qualitative and quantitative effects on the hydrocarbons detected. The data support the hypothesis that cuticular profiles of A. tumida are contingent on environment, partitioning on the basis of rearing diet and source hives. The finding has implications for the regulation of interactions between A. tumida and honeybees and improvements in targeting of management strategies.

Insight into the Ozone-Assisted Low-Temperature Combustion of Dimethyl Ether by Means of Stabilized Cool Flames.

The low-temperature combustion kinetics of dimethyl ether (DME) were studied by means of stabilized cool flames in a heated stagnation plate burner configuration using ozone-seeded premixed flows of DME/O2. Direct imaging of CH2O* chemiluminescence and laser-induced fluorescence of CH2O were used to determine the flame front positions in a wide range of lean and ultra-lean equivalence ratios and ozone concentrations for two strain rates. The temperature and species mole fraction profiles along the flame were measured by coupling thermocouples, gas chromatography, micro-chromatography, and quadrupole mass spectrometry analysis. A new kinetic model was built on the basis of the Aramco 1.3 model, coupled with a validated submechanism of O3 chemistry, and was updated to improve the agreement with the obtained experimental results and experimental data available in the literature. The main results show the efficiency of the tested model to predict the flame front position and temperature in every tested condition, as well as the importance of reactions typical of atmospheric chemistry in the prediction of cool flame occurrence. The agreement on the fuel and major products is overall good, except for methanol, highlighting some missing kinetic pathways for the DME/O2/O3 system, possibly linked to the direct addition of atomic oxygen on the fuel radical, modifying the product distribution after the cool flame.

An Innate Preference of Bumblebees for Volatile Organic Compounds Emitted by Phaseolus vulgaris Plants Infected With Three Different Viruses

Cucumber mosaic virus (CMV)-infected tomato (Solanum lycopersicum L.) plants emit volatile organic compounds (VOCs) attractive to bumblebees (Bombus terrestris L.), which are important tomato pollinators, but which do not transmit CMV. We investigated if this effect was unique to the tomato-CMV pathosystem. In two bean (Phaseolus vulgaris L.) cultivars, infection with the potyviruses bean common mosaic virus (BCMV) or bean common mosaic necrosis virus (BCMNV), or with the cucumovirus CMV induced quantitative changes in VOC emission detectable by coupled gas chromatography–mass spectrometry. In free-choice olfactometry assays bumblebees showed an innate preference for VOC blends emitted by virus-infected non-flowering bean plants and flowering CMV-infected bean plants, over VOCs emitted by non-infected plants. Bumblebees also preferred VOCs of flowering BCMV-infected plants of the Wairimu cultivar over non-infected plants, but the preference was not significant for BCMV-infected plants of the Dubbele witte cultivar. Bumblebees did not show a significant preference for VOCs from BCMNV-infected flowering bean plants but differential conditioning olfactometric assays showed that bumblebees do perceive differences between VOC blends emitted by flowering BCMNV-infected plants over non-infected plants. These results are consistent with the concept that increased pollinator attraction may be a virus-to-host payback, and show that virus-induced changes in bee-attracting VOC emission is not unique to one virus-host combination.

A GC-SSIM-CRDS system: Coupling a gas chromatograph with a Cavity Ring-Down Spectrometer for onboard Twofold analysis of molecular and isotopic compositions of natural gases during ocean-going research expeditions

Carbon dioxide (CO2) and methane (CH4) are two climate-sensitive components of gases migrating within sediments and emitted into the water column on continental margins. They are involved in several key biogeochemical processes entering into the global carbon cycle. In order to perform onboard measurements of both the molecular and stable carbon isotope ratios (δ13C) of CH4 and CO2 of natural gases during oceanic cruises, we have developed a novel approach coupling gas chromatography (GC) with cavity ring-down spectroscopy (CRDS). The coupled devices are connected to a small sample isotope module (SSIM) to form a system called GC-SSIM-CRDS. Small volumes of natural gas samples (<1 mL) are injected into the GC using a headspace autosampler or a gas-tight syringe to separate the chemical components using a Shincarbon ST packed column and for molecular quantification by thermal conductivity detection (TCD). Subsequently, CO2 from the sample is trapped in a 7 mL loop at 32 °C before being transferred to the CRDS analyzer for sequential determination of the stable carbon isotope ratios of CH4 and CO2 in 24 min. The loop is an open column (without stationary phase). This approach does not require the use of adsorbents or cooling for the trapping step. Optimization of the separation step prior to analysis was focused on the influence of two key separation factors 1) the flow of the carrier gas and 2) the temperature of the oven. Our analytical system and the measurement protocol were validated on samples collected from gas seeps in the Sea of Marmara (Turkey). Our results show that the GC-SSIM-CRDS system provides a reliable determination of the molecular identification of CH4 and CO2 in complex natural gases, followed by the stable carbon isotope ratios of methane and carbon dioxide.

Evaluation of volatile metabolites as potential markers to predict naturally-aged seed vigour by coupling rapid analytical profiling techniques with chemometrics

Rapid volatile detection methods for seed vigour rely heavily on artificial ageing (AA), however the comparability of volatile organic compounds (VOCs) to natural ageing (NA) and practicability of the detection models were not well known. In this study, VOCs between AA and NA sweet corn seeds were compared and Partial Least Squares Regression (PLS-R) modelswere constructed based on AA to predict the seed vigour of NA. A total of 33 VOCs were identified, among which aldehydes showed the highest consistency between NA and AA. Furthermore, a AS-PLS-R model with variable importance in projection (VIP > 1) and Pearson Correlation Coefficient (r > 0.9) algorithms, which was built on 3 volatile markers: benzaldehyde monomer, n-nonanal, 1-butanol monomer, achieved the best performance (R2p of 0.901 and RMSEP of 0.050). Therefore, coupling Gas Chromatography- Ion Mobility Spectrometry (GC-IMS) with chemometrics can be an effective way to monitor and predict stored seeds vigour.

Electrochemical Lithiation/Delithiation of ZnO in 3D-Structured Electrodes: Elucidating the Mechanism and the Solid Electrolyte Interphase Formation.

Conversion/alloy active materials, such as ZnO, are one of the most promising candidates to replace graphite anodes in lithium-ion batteries. Besides a high specific capacity (qZnO = 987 mAh g-1), ZnO offers a high lithium-ion diffusion and fast reaction kinetics, leading to a high-rate capability, which is required for the intended fast charging of battery electric vehicles. However, lithium-ion storage in ZnO is accompanied by the formation of lithium-rich solid electrolyte interphase (SEI) layers, immense volume expansion, and a large voltage hysteresis. Nonetheless, ZnO is appealing as an anode material for lithium-ion batteries and is investigated intensively. Surprisingly, the conclusions reported on the reaction mechanism are contradictory and the formation and composition of the SEI are addressed in only a few works. In this work, we investigate lithiation, delithiation, and SEI formation with ZnO in ether-based electrolytes for the first time reported in the literature. The combination of operando and ex situ experiments (cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction, coupled gas chromatography and mass spectrometry, differential electrochemical mass spectrometry, and scanning electron microscopy) clarifies the misunderstanding of the reaction mechanism. We evidence that the conversion and alloy reaction take place simultaneously inside the bulk of the electrode. Furthermore, we show that a two-layered SEI is formed on the surface. The SEI is decomposed reversibly upon cycling. In the end, we address the issue of the volume expansion and associated capacity fading by incorporating ZnO into a mesoporous carbon network. This approach reduces the capacity fading and yields cells with a specific capacity of above 500 mAh g-1 after 150 cycles.