Chemical Attractants Research Articles

Chimpanzee (Pan troglodytes schweinfurthii) Group Sleep and Pathogen-Vector Avoidance: Experimental Support for the Encounter-Dilution Effect

Sleep is essential for survival, yet it represents a time of extreme vulnerability, including through exposure to parasites and pathogens transmitted by biting insects. To reduce the risks of exposure to vector-borne disease, the encounter-dilution hypothesis proposes that the formation of groups at sleep sites is influenced by a “selfish herd” behavior, where individuals dilute risk by sleeping with other group members. To investigate this hypothesis in the context of chimpanzee (Pan troglodytes schweinfurthii) sleep site selection, we employed four light traps that we also baited with nontoxic chemical attractants to capture insects throughout the night. Across 74 nights with 294 traps set, we collected 66,545 individual insects. Consistent with the encounter-dilution hypothesis, we found that insect exposure, inferred by absolute numbers of insects caught in nighttime traps, was strongly influenced by the grouping of traps. Specifically, single traps caught more insects—including vector transmitting female mosquitoes—than grouped traps, and the number of insects caught increased with increasing distance between grouped traps. Moreover, ground sleep sites caught fewer insects than arboreal sleep sites. In addition, traps associated with Cynometra alexandri trees resulted in significantly lower catch rates than Pseudospondias microcarpa–associated traps. Our results suggest wild chimpanzees use group sleep as a strategy to avoid biting insects that serve as hosts for vector-borne diseases.

Experimental evidence of chemical attraction in the mutualistic zebra mussel-killer shrimp system.

Invasion facilitation, whereby one species has a positive effect on the establishment of another species, could help explain the rapid colonisation shown by some freshwater invasive species, but the underlying mechanisms remain unclear. We employed two-choice test arenas to test whether the presence of zebra mussel (Dreissena polymorpha) could facilitate the establishment of the killer shrimp (Dikerogammarus villosus). Killer shrimp preferred to settle on mats of zebra mussel, but this was unrelated to mat size, and was not different from attraction shown to artificial grass, suggesting that zebra mussel primarily provides substrate and refuge to the killer shrimp. Killer shrimp were strongly attracted to water scented by zebra mussel, but not to water scented by fish. Chemical attraction to the zebra mussel’s scent did not differ between sympatric and allopatric populations of killer shrimp, suggesting that chemical attraction is not an acquired or learned trait. Our study shows, for the first time, chemical attraction between two highly invasive freshwater species, thereby providing a plausible mechanism for invasion facilitation. This has implications for managing the spread of killer shrimp, and perhaps other freshwater invasive species, because chemical attraction could significantly increase establishment success in mutualistic systems. Failure to consider invasion facilitation may underestimate the risk of establishment, and likely also the impact of some aquatic invaders.

Diversity & tractability revisited in collaborative small molecule phenotypic screening library design

Identification of purposeful chemical matter on a broad range of drug targets is of high importance to the pharmaceutical industry. However, disease-relevant but more complex hit-finding plans require flexibility regarding the subset of the compounds that we screen. Herein we describe a strategy to design high-quality small molecule screening subsets of two different sizes to cope with a rapidly changing early discovery portfolio. The approach taken balances chemical tractability, chemical diversity and biological target coverage. Furthermore, using surveys, we actively involved chemists within our company in the selection process of the diversity decks to ensure current medicinal chemistry principles were incorporated. The chemist surveys revealed that not all published PAINS substructure alerts are considered productive by the medicinal chemistry community and in agreement with previously published results from other institutions, QED scores tracked quite well with chemists’ notions of chemical attractiveness.

Hybrid Two-Component Sensors for Identification of Bacterial Chemoreceptor Function.

Soil bacteria adapt to diverse and rapidly changing environmental conditions by sensing and responding to environmental cues using a variety of sensory systems. Two-component systems are a widespread type of signal transduction system present in all three domains of life and typically are comprised of a sensor kinase and a response regulator. Many two-component systems function by regulating gene expression in response to environmental stimuli. The bacterial chemotaxis system is a modified two-component system with additional protein components and a response that, rather than regulating gene expression, involves behavioral adaptation and results in net movement toward or away from a chemical stimulus. Soil bacteria generally have 20 to 40 or more chemoreceptors encoded in their genomes. To simplify the identification of chemoeffectors (ligands) sensed by bacterial chemoreceptors, we constructed hybrid sensor proteins by fusing the sensor domains of Pseudomonas putida chemoreceptors to the signaling domains of the Escherichia coli NarX/NarQ nitrate sensors. Responses to potential attractants were monitored by β-galactosidase assays using an E. coli reporter strain in which the nitrate-responsive narG promoter was fused to lacZ Hybrid receptors constructed from PcaY, McfR, and NahY, which are chemoreceptors for aromatic acids, tricarboxylic acid cycle intermediates, and naphthalene, respectively, were sensitive and specific for detecting known attractants, and the β-galactosidase activities measured in E. coli correlated well with results of chemotaxis assays in the native P. putida strain. In addition, a screen of the hybrid receptors successfully identified new ligands for chemoreceptor proteins and resulted in the identification of six receptors that detect propionate.IMPORTANCE Relatively few of the thousands of chemoreceptors encoded in bacterial genomes have been functionally characterized. More importantly, although methyl-accepting chemotaxis proteins, the major type of chemoreceptors present in bacteria, are easily identified bioinformatically, it is not currently possible to predict what chemicals will bind to a particular chemoreceptor. Chemotaxis is known to play roles in biodegradation as well as in host-pathogen and host-symbiont interactions, but many studies are currently limited by the inability to identify relevant chemoreceptor ligands. The use of hybrid receptors and this simple E. coli reporter system allowed rapid and sensitive screening for potential chemoeffectors. The fusion site chosen for this study resulted in a high percentage of functional hybrids, indicating that it could be used to broadly test chemoreceptor responses from phylogenetically diverse samples. Considering the wide range of chemical attractants detected by soil bacteria, hybrid receptors may also be useful as sensitive biosensors.

Collective behaviour in 480-million-year-old trilobite arthropods from Morocco

Interactions and coordination between conspecific individuals have produced a remarkable variety of collective behaviours. This co-operation occurs in vertebrate and invertebrate animals and is well expressed in the group flight of birds, fish shoals and highly organized activities of social insects. How individuals interact and why they co-operate to constitute group-level patterns has been extensively studied in extant animals through a variety mechanistic, functional and theoretical approaches. Although collective and social behaviour evolved through natural selection over millions of years, its origin and early history has remained largely unknown. In-situ monospecific linear clusters of trilobite arthropods from the lower Ordovician (ca 480 Ma) of Morocco are interpreted here as resulting either from a collective behaviour triggered by hydrodynamic cues in which mechanical stimulation detected by motion and touch sensors may have played a major role, or from a possible seasonal reproduction behaviour leading to the migration of sexually mature conspecifics to spawning grounds, possibly driven by chemical attraction (e.g. pheromones). This study confirms that collective behaviour has a very ancient origin and probably developed throughout the Cambrian-Ordovician interval, at the same time as the first animal radiation events.

Interfacial Segregation of Alloying Elements During Dissimilar Ultrasonic Welding of AA6111 Aluminum and Ti6Al4V Titanium

Ultrasonic welding is a promising technique for joining dissimilar metals. A particular metal combination of interest to the automotive industry is aluminum-titanium. In such welds, performance is often controlled by processes at the interface, including segregation and intermetallic precipitate formation. This study used high-resolution electron microscopy to investigate this in detail. Enrichment of silicon, magnesium, and oxygen were found at ultrasonic welded aluminum/titanium interfaces; however, other alloying elements such as copper and V were not segregated. Surprisingly, in a very short welding time (1.4 seconds), ~ 4 at. pct of Si was found at the Al/Ti interface. The segregated Si distribution varied inversely with that of O and Mg. The residual oxides and the segregated Si on the Al/Ti interface may act as a barrier for Al3Ti nucleation and growth. The strong chemical attraction between Ti and Si is probably the driving force for Si segregation to the Al/Ti interface. The presence of discontinuous oxides at the Al/Ti weld interface may deteriorate the mechanical properties of the weld.

Graphene oxide can prevent mosquito bites

Mosquitoes are the deadliest animals on the planet, killing at least 725,000 people every year by passing diseases through their bites, according to the Barcelona Institute for Public Health. The US Department of Defense is interested in a nonpesticide mosquito deterrent for its personnel, and a team of researchers from Brown University has possibly found one. At the ACS meeting, Cintia J. Castilho reported that a 1 µm thick layer of graphene oxide (GO) physically and chemically deters Aedes aegypti—the mosquito that carries yellow fever. The researchers expected that mosquitoes could not physically bite a person through the dry GO layer, Castilho said. However, they were surprised that the mosquitoes didn’t land as much on dry GO patches placed on people’s arms. This finding suggests that the thin layer is impermeable to chemical attractants released by people, such as CO2, while still remaining breathable by letting water pass through. Mosquitoes

Discontinuous phase transition in chemotactic aggregation with density-dependent pressure.

Many small organisms such as bacteria can attract each other by depositing chemical attractants. At the same time, they exert repulsive force on each other when crowded, which can be modeled by effective pressure as an increasing function of the organisms' density. As the chemical attraction becomes strong compared to the effective pressure, the system will undergo a phase transition from homogeneous distribution to aggregation. In this work, we describe the interplay of organisms and chemicals on a two-dimensional disk with a set of partial differential equations of the Patlak-Keller-Segel type. By analyzing its Lyapunov functional, we show that the aggregation transition occurs discontinuously, forming an aggregate near the boundary of the disk. The result can be interpreted within a thermodynamic framework by identifying the Lyapunov functional with free energy.

Diversity and population dynamic of Tabanidae (Diptera) in the cerrado-pantanal ecotone

Tabanid (Diptera) species are associated with the mechanical transmission of several pathogens to both domestic and wild animals around the world. The aim of this study was to evaluate the diversity, abundance, and seasonal dynamic of tabanids in the Cerrado-Pantanal ecotone in Miranda, state of Mato Grosso do Sul, Brazil. Tabanids were collected once a month, from June 2001 to May 2003, for seven consecutive days per collection, using canopy and nzi type traps baited with a chemical attractant (1-octen-3-ol). A total of 6,492 individuals from 39 species and 18 genera was collected, which increases from 25 to 34 the number of tabanid species reported for the studied region. Tabanus occidentalis Linnaeus, 1758 (62.21%) was the most abundant species throughout the collection period, followed by Lepiselaga crassipes (Fabricius, 1805) (7.19%) and Tabanus sorbillans Wiedemann, 1828 (5.68%). The peak of the tabanid population was reached during the rainy season, which is the period of the highest potential risk of mechanical transmission of pathogens by these insects in the studied region.

Molybdenum-mediated chemotaxis of Pseudoalteromonas lipolytica enhances biofilm-induced mineralization on low alloy steel surface

Formation of biofilm and the subsequent biomineralization on the steel surface are highly influenced by the steel surface properties. Molybdenum (Mo) is a commonly used metal in steel, which can improve its strength and resistance to corrosion. Herein, the effect of Mo on the biomineralization process was investigated by designing low alloy steels containing different concentrations of Mo. Surface characterization showed that moderate concentrations of Mo (such as 0.6 wt%) significantly enhanced the biofilm formation and the mineralization process. Mechanistically, it is demonstrated that Mo ions served as a chemical attractant for Pseudoalteromonas lipolytica and activated the chemotaxis pathway.

Efficient capture of iodine by a polysulfide-inserted inorganic NiTi-layered double hydroxides

Effective capture of radioactive iodine is highly desirable but still remains a significant challenge. We reported here a polysulfide (Sx2−) intercalated inorganic cationic Ni-Ti layered double hydroxide, NiTi-Sx-LDH, which was prepared by coprecipitation method and ion exchange method for efficient capture of iodine. Due to the strong chemical attraction between the soft Lewis base Sx2− and the soft Lewis acid I2, and the reducing property of Sx2−, NiTi-Sx-LDH exhibits highly efficient iodine capture. During the adsorption process, I2 is reduced to I3− by the intercalated Sx2−. In combination with chemical adsorption and physical adsorption, the adsorption capacity of NiTi-Sx-LDH to iodine vapor reaches 52% (wt%). In addition, the adsorption properties of NiTi-Sx-LDH on elemental iodine in organic solvent cyclohexane were also studied, and the maximum adsorption capacity of NiTi-Sx-LDH for iodine reaches up to 527.4 mg/g. Compared with various sorbents for iodine, it is cost-effective, capable of achieving scale-up preparation, and the good performance for the iodine adsorption suggests that NiTi-Sx-LDH may be considered as a promising sorbent for efficient removal of radioactive iodine from reprocessing plant off-gas streams.

A green and low-cost hollow gangue microsphere/geopolymer adsorbent for the effective removal of heavy metals from wastewaters

In this paper, hollow gangue microspheres (GM) were introduced into a geopolymer matrix through a geopolymeric method; our aim was to synthesize a green and low-cost adsorbent (GM/KGP) for the removal of heavy metal ions (Cu2+, Cd2+, Zn2+, and Pb2+) from aqueous solutions. We investigated the microstructure of the GM/KGP adsorbent, as well as the effects of adsorbent dose, time, and temperature on adsorption behavior; moreover, an adsorption mechanism was proposed. The GM/KGP adsorbent possessed a typical broad amorphous structure and abundant O-containing functional groups on its surface. The adsorption of Cu2+, Cd2+, Zn2+, and Pb2+ onto the GM/KGP adsorbent fitted well to the pseudo-second-order kinetic model, while the equilibrium isotherm adsorption data were fitted well to the Langmuir equation. The adsorption mechanism GM/KGP was attributed to physical, chemical, and electrostatic attractions, as well as to ion exchange. We conclude that this novel adsorbent has great potential in removing heavy metal ions from contaminated wastewater.

Trimellitic acid functionalized magnetite nanoparticles for the efficient removal of Pb(II) and Cr(VI) from wastewater streams

Silica-coated Fe3O4 nanoparticles were prepared and functionalized with trimellitic anhydride generating novel amide and two acid moieties on the surface of the nanoparticles. These nanoparticles were found to be ferrimagnetic with average particle size 50–60 nm as characterized by XRD, SEM, EDS, VSM and FTIR analyses. The functionalized nanoparticles were exploited as adsorbent for the removal of Pb(II) cations and Cr(VI) anions from their aqueous solutions and uptake of metal ions was monitored by atomic absorption spectroscopy (AAS). These nanoparticles were found to be more effective for the removal of Pb(II) cations due to the negatively charged surface groups relative to Cr(VI) anions. The adsorption data fitted well with Langmuir as well as Freundlich adsorption isotherms, showing a complex nature of adsorption phenomena, comprising electrostatic as well as chemical attraction between surface groups and metal ions. The metal bearing nanoparticles were easily separated from the solution by simply applying external magnetic field.

Global well-posedness and asymptotic behavior in Besov-Morrey spaces for chemotaxis-Navier-Stokes fluids

In this work, we consider the Keller-Segel system coupled with Navier-Stokes equations in RN for N ≥ 2. We prove the global well-posedness with small initial data in Besov-Morrey spaces. Our initial data class extends previous ones found in the literature such as that obtained by Kozono, Miura, and Sugiyama [J. Funct. Anal. 270(5), 1663–1683 (2016)]. It allows us to consider initial cell density and fluid velocity concentrated on smooth curves or at points depending on the spatial dimension. Self-similar solutions are obtained depending on the homogeneity of the initial data and considering the case of a chemical attractant without the degradation rate. Moreover, we analyze the asymptotic stability of solutions at infinity and obtain a class of asymptotically self-similar ones.

Exploiting the Synergistic Effect of Kairomones and Light-Emitting Diodes on the Attraction of Phlebotomine Sand Flies to Light Traps in Brazil.

The synergistic effect of light-emitting diodes (LEDs) and kairomones on the attraction of sand flies to light traps was evaluated. Octenol and lactic acid were used as chemical attractants. Green LEDs and the incandescent lamps were used as light attractants. Five CDC-type light traps with the respective combination of attractants (incandescent lamp, incandescent lamp + chemical attractant, green LED, green LED + chemical attractant, and chemical attractant alone [without light]) were set between 18:00 and 06:00 following a Latin square design. A total of 6,536 sand flies and 16 species were collected. The most frequent species collected was Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera, Psychodidae) accounting for 43.21% of all individuals. Order of success (mean, SD) of lactic acid attractant fly capture was as follows: LED + lactic acid (36.83 ± 4.74), LED alone (34.87 ± 4.61), incandescent lamp + lactic acid (22.80 ± 3.19), incandescent lamp alone (12.67 ± 2.03), and lactic acid (0.46 ± 0.13). Order of success of octenol attractant fly capture was as follows: LED + octenol (37.23 ± 5.61), LED alone (35.77 ± 5.69), incandescent lamp + octenol (18.63 ± 3.28), incandescent lamp alone (14.67 ± 2.86), and octenol alone (1.80 ± 0.65). With exception of lactic acid + incandescent light, chemical synergists played no part in significantly increasing light trap capture of phlebotomine sand flies. However, the use of LEDs, with or without such attractants, provided significantly higher capture compared to the incandescent lamp with or without such chemicals, showing that LEDs are suitable and efficient light sources for surveillance and monitoring of phlebotomine sand flies in Brazil.

Capacitive Deionization Systems for Water Desalination Applications: Role of the Electrosorption Resistance and Non-Electrostatic Binding in the Porous Electrodes

The unprecedented global water scarcity and shortage of fresh water have drawn attention to an abundant yet overlooked water resource: Brackish ground water. Although the common desalination methods are energy intensive for low salinity water streams, Capacitive Deionization (CDI) offers a highly efficient and economical alternative for desalinating brackish water. In CDI, an electrically charged porous material is employed to remove ionic species from aqueous solutions. CDI includes different multi-scale transport phenomena and requires robust theories to accurately model its performance. In this work, we introduce a dynamic two-dimensional model which couples the diffusion and advection in the bulk solution with the diffusion and electrosorption in the porous material. The significance of this model lies in the incorporation of the transport theories with the adsorption/desorption resistances and non-constant chemical attraction forces in the micropores. A lab-scale CDI unit is employed to validate the proposed model at different transport time scales and electrochemical techniques are used to characterize these systems. Efficiency of the studied cases is also evaluated using the proposed inclusive figure-of-merits, where both numerical and experimental data present a trade-off between adsorption and energetic performance of the systems with low and high mass Péclet number. The results obtained here highlight the significant role of the rate limiting resistance for the ionic species transferring from macropores into the micropores in the porous electrode, especially at low initial concentrations.

Selective H2S-sensing performance of Si nanowires through the formation of ZnO shells with Au functionalization

A novel gas sensor fabricated from ZnO-shelled Si nanowires (SiNWs) is presented. After coating a thin layer of Au on the surfaces of Si NWs, ZnO layers were formed on the surfaces of p-SiNWs by thermal evaporation of Zn powders and a subsequent oxidation process. Microscopic analysis confirmed the successful formation of ZnO-Si core-shell NWs with Au nanoparticles present on the shell surface. The gas sensing performance of the gas sensor fabricated using the p-Si/n-ZnO core-shell NWs was evaluated for various gases. The sensor exhibited outstanding response and selectivity to H2S gas. The gas sensing mechanism was evaluated in detail and attributed to various factors, including the formation of ZnO/Si and Au/ZnO heterojunctions and the chemical attraction between ZnO and Au. The results demonstrate a new sensing material for H2S detection in various fields that can be easily incorporated into Si-based devices.

Effect of the mating plug on female chemical attractiveness and mating acceptance in a scorpion

AbstractAfter mating, females may experience a decline in sexual receptivity and attractiveness that may be associated with changes in the production and emission of sex pheromones. In some cases, these changes are produced by chemical substances or structures (e.g., mating plugs) produced by males as a strategy to avoid or reduce sperm competition. In scorpions, sex pheromones may be involved in finding potential mates and starting courtship. Here, we tested the hypothesis that the males ofUrophonius brachycentrus, a species that produces a mating plug, use chemical communication (sex pheromones) to detect, localize, and discriminate females according to their mating status (virgin or inseminated), aided by chemical signaling. We also explored the effect of extracting of the mating plug on chemical communication and mating acceptance. We used Y‐maze olfactometers with different stimuli to analyze male choice and exploration time. To evaluate mating acceptance, we measured the attractiveness and receptivity of females of different mating status. We found that chemical communication occurs through volatile pheromones, but not contact pheromones. Males equally preferred sites with virgin or inseminated females with removed mating plug. In turn, females with these mating statuses were more attractive and receptive for males than inseminated females. This study suggests that the mating plug significantly affects female chemical attractiveness with an effect on volatile pheromones and decreasing sexual mating acceptance of females. The decline in the female's sexual receptivity is a complex process that may respond to several non‐exclusive mechanisms imposed by males and strategically modulated by females.

MOOCs as 'chemical attractants'


 
 
 
 This study explores the outcomes of a chemistry MOOC, delivered on two occasions through the FutureLearn platform. Learner background and course feedback, including managing the expectations of potential participants, course facilitation, the importance of having a strong presence on the forums and the tutor having a ‘face’, is explored. The findings will be especially relevant to practitioners interested in learning more about how MOOCs could contribute to a university strategy for internationalisation, widening participation and public engagement. It adds to the growing literature on an educator’s experience, providing an insight into the rewards and challenges of teaching in MOOCs, and aims to encourage and support other higher education providers considering developing related online courses. 
 
 
 

Kinetic non-reversibility of the cracking reactions and its accounting during mathematical modeling of industrial process

The paper presents the approach to the catalytic cracking modeling with consideration of the reactions’ reversibility/non-reversibility depending on the current concentrations and the cracking temperature. The thermodynamic analysis of the reactions using the quantum-chemical methods allows formulating a hydrocarbons conversion scheme at the thermal equilibrium temperature between the feedstock and the catalyst. The magnitude of the current chemical attraction of reactions is a criterion of thermodynamic non-reversibility of reactions, which is determined at each stage of the calculation. It has been shown that the change in the concentrations of conversion participants and cracking temperature have a significant effect on the catalytic cracking reactions. Thus, the cyclization reactions are non-reversible up to 512.9 °C (Arij = 6.46 kJ/mol) during the processing of feedstock with saturated hydrocarbons to aromatics ratio is 2.1 and with further temperature increasing the contribution of reverse reactions rises. Also with increasing the saturated hydrocarbons to aromatics ratio from 2.1 to 3.2 in the feedstock, the equilibrium of the reaction shifts to low temperatures from 512.9 to 508.9 °C (Arij = 6.497 kJ/mol). It is connected with the fact that intensification of the exotermic reactions (alkylation, condensation, coke formation) under certain conditions is possible. It is an important factor in terms of catalyst deactivation and has an effect on the desired product yield.