A simple Gause‐type predator–prey model considering social predation

The consumer–resource relationships are among the most fundamental of all ecological relationships and have been the focus of ecology since its beginnings. Usually are described by nonlinear differential equation systems, putting the emphasis in the effect of antipredator behavior (APB) by the prey; nevertheless, a minor quantity of articles has considered the social behavior of predators. In this work, two predator–prey models derived from the Volterra model are analyzed, in which the equation of predators is modified considering cooperation or collaboration among predators. It is well known that competition among predators produces a stabilizing effect on system describing the model, since there exists a wide set in the parameter space where the system has a unique equilibrium point in the phase plane, which is globally asymptotically stable. Meanwhile, the cooperation can originate more complex and unusual dynamics. As we will show, it is possible to prove that for certain subset of parameter values the predator population sizes tend to infinite when the prey population goes to extinct. This apparently contradicts the idea of a realistic model, when it is implicitly assumed that the predators are specialist, ie, the prey is its unique source of food. However, this could be a desirable effect when the prey constitutes a plague. To reinforce the analytical result, numerical simulations are presented.     

Sustainable Synthesis of the Naturally Hypolipidemic Agent α-Asarone

A short and practical preparation of α-asarone was developed using the inexpensive methylisoeugenol as a starting material. The utilization of a sequence of tribromination, debromination, and copper-mediated aromatic substitution enabled the stereoselective formation of only the E-isomer of α-asarone in good yield.     

ZnSe Etching of Zn‐Rich Cu2ZnSnSe4: An Oxidation Route for Improved Solar‐Cell Efficiency

Cu₂ZnSnSe₄ kesterite compounds are some of the most promising materials for low‐cost thin‐film photovoltaics. However, the synthesis of absorbers for high‐performing devices is still a complex issue. So far, the best devices rely on absorbers grown in a Zn‐rich and Cu‐poor environment. These off‐stoichiometric conditions favor the presence of a ZnSe secondary phase, which has been proved to be highly detrimental for device performance. Therefore, an effective method for the selective removal of this phase is important. Previous attempts to remove this phase by using acidic etching or highly toxic organic compounds have been reported but so far with moderate impact on device performance. Herein, a new oxidizing route to ensure efficient removal of ZnSe is presented based on treatment with a mixture of an oxidizing agent and a mineral acid followed by treatment in an aqueous Na₂S solution. Three different oxidizing agents were tested: H₂O₂, KMnO₄, and K₂Cr₂O₇, combined with different concentrations of H₂SO₄. With all of these agents Se^2? from the ZnSe surface phase is selectively oxidized to Se⁰, forming an elemental Se phase, which is removed with the subsequent etching in Na₂S. Using KMnO₄ in a H₂SO₄‐based medium, a large improvement on the conversion efficiency of the devices is observed, related to an improvement of all the optoelectronic parameters of the cells. Improvement of short‐circuit current density (J_sc) and series resistance is directly related to the selective etching of the ZnSe surface phase, which has a demonstrated current‐blocking effect. In addition, a significant improvement of open‐circuit voltage (V_oc), shunt resistance (R_sh), and fill factor (FF) are attributed to a passivation effect of the kesterite absorber surface resulting from the chemical processes, an effect that likely leads to a reduction of nonradiative‐recombination states density and a subsequent improvement of the p–n junction.     

Thermogravimetric analysis of the water vapor addition during the CaO carbonation process at moderate temperatures (40–70 °C)

Experiments were performed on calcium oxide, using water vapor with N₂ or CO₂ as carrier gases, between 40 and 70 °C. A initial experiment was performed with water vapor in the presence of N₂ to elucidate the possible hydroxylation process produced by water vapor exclusively. On the other hand, when CO₂ was used as carrier gas the CaO reactivity changed, producing different hydrated, hydroxylated, and carbonated phases. On the basis of these results and the fact that under dry conditions CO₂ is not absorbed on CaO at T < 70 °C, a possible CaO–H₂O–CO₂ reaction mechanism was proposed, where CaO superficial hydroxylation process seems to play a very important role during the CO₂ capture. Finally, a kinetic analysis was produced to compare the temperature and humidity relative influence on the whole process.     

Recent Advances in Luminescent Recognition and Chemosensing of Iodide in Water

This Minireview covers the latest developments of chemosensors based on transition‐metal receptors and organic fluorophores with specific binding sites for the luminescent detection and recognition of iodide in aqueous media and real samples. In all selected examples within the last decade (made‐post 2010), the iodide sensing and recognition is probed by monitoring real‐time changes of the fluorescence or phosphorescence properties of the chemosensors. This review highlights effective strategies to iodide sensing from a structural approach where the iodide recognition/sensing process, through supramolecular interactions as coordination bonds, hydrogen bonds, halogen bonds and electrostatic interactions, is transduced into an optical change easily measurable. The selective iodide sensing is an active field of research with global interest due to the importance of iodide in biological, medicinal, industrial, environmental and chemical processes.     

Effects of Ornamental Plant Density and Mineral/Plastic Media on the Removal of Domestic Wastewater Pollutants by Home Wetlands Technology

Wastewater treatment (WWT) is a priority around the world; conventional treatments are not widely used in rural areas owing to the high operating and maintenance costs. In Mexico, for instance, only 40% of wastewater is treated. One sustainable option for WWT is through the use of constructed wetlands (CWs) technology, which may remove pollutants using cells filled with porous material and vegetation that works as a natural filter. Knowing the optimal material and density of plants used per square meter in CWs would allow improving their WWT effect. In this study, the effect of material media (plastic/mineral) and plant density on the removal of organic/inorganic pollutants was evaluated. Low (three plants), medium (six plants) and high (nine plants) densities were compared in a surface area of 0.3 m² of ornamental plants (Alpinia purpurata, Canna hybrids and Hedychium coronarium) used in polycultures at the mesocosm level of household wetlands, planted on the two different substrates. Regarding the removal of contaminants, no significant differences were found between substrates (p ≥ 0.05), indicating the use of plastic residues (reusable) is an economical option compared to typical mineral materials. However, differences (p = 0.001) in removal of pollutants were found between different plant densities. For both substrates, the high density planted CWs were able to remove COD in a range of 86–90%, PO₄-P 22–33%, NH₄-N in 84–90%, NO₃-N 25–28% and NO₂-N 38–42%. At medium density, removals of 79–81%, 26–32, 80–82%, 24–26%, and 39–41%, were observed, whereas in CWs with low density, the detected removals were 65–68%, 20–26%, 79–80%, 24–26% and 31–40%, respectively. These results revealed that higher COD and ammonia were removed at high plant density than at medium or low densities. Other pollutants were removed similarly in all plant densities (22–42%), indicating the necessity of hybrid CWs to increase the elimination of PO₄-P, NO₃-N and NO₂-N. Moreover, high density favored 10 to 20% more the removal of pollutants than other plant densities. In addition, in cells with high density of plants and smaller planting distance, the development of new plant shoots was limited. Thus, it is suggested that the appropriate distance for this type of polyculture plants should be from 40 to 50 cm in expansion to real-scale systems in order to take advantage of the harvesting of species in these and allow species of greater foliage, favoring its growth and new shoots with the appropriate distance to compensate, in the short time, the removal of nutrients.     

Spatially Controlled Supramolecular Polymerization of Peptide Nanotubes by Microfluidics

Despite the importance of spatially resolved self‐assembly for molecular machines, the spatial control of supramolecular polymerization with synthetic monomers had not been experimentally established. Now, a microfluidic‐regulated tandem process of supramolecular polymerization and droplet encapsulation is used to control the position of self‐assembled microfibrillar bundles of cyclic peptide nanotubes in water droplets. This method allows the precise preferential localization of fibers either at the interface or into the core of the droplets. UV absorbance, circular dichroism and fluorescence microscopy indicated that the microfluidic control of the stimuli (changes in pH or ionic strength) can be employed to adjust the packing degree and the spatial position of microfibrillar bundles of cyclic peptide nanotubes. Additionally, this spatially organized supramolecular polymerization of peptide nanotubes was applied in the assembly of highly ordered two‐dimensional droplet networks.     

Influence of dielectric barrier plasma treatment of ZnMgAl alloy-coated steel on the adsorption of organophosphonic acid monolayers

The adsorption of octadecyl phosphonic acid (ODPA) on oxide-covered surfaces of ZnMgAl alloy coatings is described as a function of a dielectric barrier discharge (DBD) pretreatment step. The ODPA monolayer formation enables the investigation of the influence of the DBD treatment on the resulting interfacial bond formation and surface coverage. Surface characterisation by means of surface spectroscopy (PM-IRRAS, XPS) and surface electrochemistry (cyclic voltammetry) showed that the DBD pretreatment with Ar, Ar/O₂ and Ar/H₂O gas mixtures leads to improved barrier properties of the adsorbed ODPA monolayer. Moreover, during ODPA monolayer formation from ethanolic solution, a partial etching of the surface oxide layer occurs.     

The Neumann and Young equations for nematic contact lines

The Neumann and Young equations for three-phase nematic contact lines have been derived using the momentum balance equation and classical liquid crystal physics theories. The novel finding is the presence of bending forces, originating from the anchoring energy of nematic interfaces, and acting on the contact line. The classical Neumann triangle or tensile force balance becomes in the presence of a nematic phase the Neumann pentagon, involving the usual three tensile forces and two additional bending forces. The Young equation that describes the static contact angle of a fluid in contact with a rigid solid is again a tensile force balance along the solid, but for nematics it also involves an additional bending force. The effects of the bending forces on contact angles and wetting properties of nematic liquid crystals are thoroughly characterized. It is found that in terms of the spreading coefficient, bending forces enlarge the partial wetting window that exists between dewetting and spontaneous spreading. Bending forces also affect the behaviour of the contact angle, such that spreading occurs at contact angles greater than zero and dewetting at values greater than pi. Finally, the contact angle range in the partial wetting regime is always less than pi.