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Green manures are a promising alternative for achieving the sustainable production of maize in the face of low soil fertility and increasingly long canicule periods, particularly in rainfed systems associated with the reproduction of local agrobiodiversity. However, it is necessary to investigate what are the advantages and disadvantages associated with different species of native and exotic pulse, as well as their overall contribution to the sustainable production of maize landraces. In order to do so, we followed the MESMIS method to assess five species of pulse (three native and two exotic) grown with maize in two plots with different soil conditions. This was done in the seasons of 2017 and 2018 the municipality of Villa de Zaachila, Oaxaca, a site with remarkable biological, agricultural and cultural diversity. A fully randomized complete block design was implemented with 11 treatments and three repetitions in the two plots. The output variables of the experiment were: land equivalence ratio, interspecific aggressiveness, content of soil organic matter, decomposition rate, plant survival rate and plant dry biomass. We also evaluated quantitative or qualitative indicators of cost, adaptability and contribution to food security. For all the possible maize-pulse combinations, except for one, polyculture outperformed maize and pulse monocultures. Exotic pulses (Crotalaria junscens spp. and Dolicho lablab) had a better performance in biomass, reincorporation of organic matter and possible nitrogen fixation, as well as greater resistance to drought in the second cycle. The native pulses (Phaseolus vulgaris and Phaseolus coccineus), however, had a greater acceptance and economic output and are important for the food security in our study site. Our results provide quantitative and qualitative elements to design combined schemes of green manures associated with maize that would help tackle current challenges regarding maize productivity, food security and response to climate change.
We present the description of a new species of genus Timea and the re-description of T. hechteli from cryptic habitats in the Gulf of Mexico. Timea alcoladoi sp. nov. is an encrusting, pale orange sponge, with megascleres ranging from styles to subtylostyles (185–990 μm long) and a single category of microscleres, spherostrongilaster characterized by a prominent rounded centre (5–15 μm in diameter). Timea hechteli was established by Lehnert & Heimler, based on the description of a very small specimen, previously recorded as Halicometes stellata by Little, and transferred to the genus Timea by Hechtel. However, because the name ‘stellata’ was preoccupied by the type species, T. stellata, the species was renamed T. hechteli, to honour George Hechtel. After the revision of Little's material and new material, we present the re-description of T. hechteli. For both species, partial sequences of COI mtDNA and ITS1-5.8S-ITS2 rDNA region were obtained in order to complement our morphological taxonomy and establish their molecular systematic position among tethyids. Tree topologies for both loci were congruent by grouping together our species as a sister group of the main Tethyida clade, which is according to the current systematics of the group. The COI fragment showed Timea as polyphyletic due to two sequences of Timea (from GenBank) that were clustered with other sponge groups. The species described here are the first record of the genus Timea from the Mexican coast of the Gulf of Mexico. A taxonomic key for West Atlantic Timea species is also presented.
Young children’s questions are ubiquitous around the world, yet question–asking and –answering are cultural practices; we must investigate cultural variation in how these practices develop rather than assume that certain practices are universal. We question an assumption in the literature that children from families of lower income or schooling have “deficits” in cognitive development. In this chapter, we critique deficit approaches and review cross–cultural studies of children’s questions within the frame of avoiding deficit assumptions. We then present findings regarding children’s questions from two studies of family conversation in different communities: a diary study of children’s spontaneous conversations about nature, and a study of parent–child conversations in a sink–and–float prediction task. In both studies, contrary to deficit ideas, we found evidence that children whose parents have lower levels of schooling showed evidence of more science–related reasoning in their questions than did those from the higher schooling group – children in the “basic schooling” group asked more explanation-seeking (not fact–seeking) questions in one study, and more conceptual (not procedural) questions in the other. Asking questions may be a cultural universal, yet our findings reveal diversity and raise questions about normativity, as well as how to define sophisticated reasoning.
Previously, we showed that disinfection of sink drains is effective at decreasing bacterial loads. Here, we report our evaluation of the ideal frequency of sink-drain disinfection and our comparison of 2 different hydrogen peroxide disinfectants.
This study assessed the in vitro anthelmintic (AH) activity of methanol and acetone:water leaf extracts from Annona squamosa, A. muricata and A. reticulata against Haemonchus contortus eggs. The egg hatch test was used to determine the effective concentrations required to inhibit 50% of eggs hatching (EC50). The role of polyphenols on AH activity was measured through bioassays with and without polyvinylpolypyrrolidone (PVPP). Methanolic extracts mainly caused the death of eggs at the morula stage (ovicidal activity). Meanwhile, acetone:water extracts caused egg-hatching failure of developed larvae (larvae failing eclosion (LFE) activity). The lowest EC50 values against H. contortus eggs were observed for the methanolic extracts from A. reticulata and A. muricata (274.2 and 382.9 µg/ml, respectively). From the six extracts evaluated, the methanolic extracts of A. muricata, A. reticulata and A. squamosa showed the highest ovicidal activity, resulting in 98.9%, 92.8% and 95.1% egg mortality, respectively. When the methanolic extract of A. squamosa was incubated with PVPP, its AH activity increased. Similarly, when acetone:water extracts of A. muriata and A. reticulata were incubated with PVPP, their LFE activity increased. Alkaloids were only evident in methanolic extracts, irrespective of PVPP incubation. The presence of acetogenins was not observed. In conclusion, methanolic extracts obtained from leaves of A. muricata, A. reticulata and A. squamosa showed ovicidal activity affecting the morula of H. contortus eggs, with minor LFE activity. Meanwhile, acetone:water extracts showed mostly LFE activity, with a lower proportion of ovicidal activity.
We study the differentiability properties of the topological equivalence between a uniformly asymptotically stable linear nonautonomous system and a perturbed system with suitable nonlinearities. For this purpose, we construct a homeomorphism inspired in the Palmer's one restricted to the positive half line, studying additional continuity properties and providing sufficient conditions ensuring its Cr–smoothness.
In recent years, modified graphene has been used in various biomedical applications due to its excellent properties that allow the development of devices capable of detecting macromolecules within the human organism, also for biomolecular analysis, discovery of biomarkers, bioimaging and target delivery. These applications involve interactions between enzymes, proteins, peptides, DNA, RNA, etc. and modified graphene, therefore the study and the theoretical and experimental investigation of these interactions is essential for the development of nanobio-technology. For example, many applications based on using modified graphene to detect macromolecules require studying the changes in the properties of doped graphene when interacting with macromolecules. In this work, DFT and molecular dynamics methods were used to obtain results of the changes in energy density of states of graphene doped with iron when it is made to interact with coenzyme A. Besides, we presented a study of molecular dynamics in order to determine the quantum factors that guide the interaction graphene-coenzyme A. The system was studied in aqueous medium which it was simulated by the dielectric constant of water. The results confirm that the methodology presented in this work can be used to theoretically detect various macromolecules.
Polypyrrole (PPy) thin films were synthetized by plasma and simultaneously doped with Iodine to enhance electromagnetic absorption and charge transfer capability in a resistive coupling cylindrical reactor. Pyrrole monomer and Iodine were the principal reagents used and the chemical reactions were created by high frequency plasma. Micrographs show an irregular surface formed by semi-spherical protrusions with tiny particles in the PPy/I samples and a rather smooth surface with wrinkles and less participation of tiny particles to PPy ones. Infrared spectroscopy analysis reveals important absorption peaks at 3253, 2932, 1668 and 635 cm-1 corresponding to the chemical bonds N-H and C-H, C-H aliphatic, C=C and C-I, respectively, belonging to the chemical structure of Pyrrole. Electrical conductivity of PPy increased from 10-10 to 10-8 S/cm due to Iodine doping. Electromagnetic absorption showed a higher response between 340 and 800 nm in the visible region. Activation energy was calculated in the range from -0.09 to 0.49 eV.
As apex predators, sharks are known to play an important role in marine food webs. Detailed information on their diet and trophic level is however needed to make clear inferences about their role in the ecosystem. A total of 335 stomachs of smooth hammerhead sharks, Sphyrna zygaena, were obtained from commercial fishing vessels operating in the Ecuadorian Pacific between January and December 2004. A total of 53 prey items were found in the stomachs. According to the Index of Relative Importance (%IRI), cephalopods were the main prey (Dosidicus gigas, Sthenoteuthis oualaniensis, Ancistrocheirus lesueurii and Lolliguncula [Loliolopsis] diomedeae). Sphyrna zygaena was thus confirmed to be a teutophagous species. The estimated trophic level of S. zygaena was between 4.6 and 5.1 (mean ± SD: 4.7 ± 0.16; males: 4.7; females: 4.8). Levin's index (BA) was low (overall: 0.07; males: 0.08; females: 0.09), indicating a narrow trophic niche. We found that sharks <150 cm in total length consumed prey of coastal origin, whereas sharks ≥150 cm foraged in oceanic waters and near the continental shelf. The analyses indicate that S. zygaena is a specialized predator consuming mainly squids.
This work presents a study about synthesis of polypyrrole films electrochemically doped with iodine by luminescent discharge plasma in aqueous sodium sulfate solution, and its structural, morphological and electrical characterization. The synthesis is carried out at atmospheric pressure with square pulse from -1.06 to 1.16 V for 120 minutes. Doping times of the films are 10, 30 and 50 minutes. The films have thicknesses of 6, 12.7, 20.32 and 25.4 μm, and linear growth trend according to the time exposure of their synthesis. The main chemical groups exhibited in the films are C-H, N-H and CH2I, which are characteristics of film doped with Iodine. The electrical conductivity calculated of polypyrrole films is in the range 10-5-10-3 S/cm, and its activation energy is between 0.052 and 1.77 eV.
This work presents a study of the chemical structure, morphology, electromagnetic absorption and electric conductivity of thin films. The electrochemical synthesis of polypyrrole/surfactant (PPy/SDS) films doped with iodine is carried out by glow discharge plasma in aqueous solution, at different reaction times. The morphology shows agglomerations of particles dispersed in the surface. Infrared spectroscopic analysis shows absorption on the wavenumbers 2915,2362 and 2082 cm-1 corresponding to chemical groups C-H, C=O and R/N=C=S, respectively. The electromagnetic absorption had higher response sensitivity between 340 to 800 nm in the visible region, and the electric conductivity of samples oscillated between 5.0x10-6 and 2.0x10-5 S/cm. The thickness films significantly increased when doping with iodine, reaching values up to 50 μm.
We explore the relationship between capacity for collective action and representation in autocracies with data from Imperial Russia. Our primary empirical exercise relates peasant representation in new institutions of local self-government to the frequency of peasant unrest in the decade prior to reform. To correct for measurement error in the unrest data and other sources of endogeneity, we exploit idiosyncratic variation in two determinants of peasant unrest: the historical incidence of serfdom and religious polarization. We find that peasants were granted less representation in districts with more frequent unrest in preceding years—a relationship consistent with the Acemoglu-Robinson model of political transitions and inconsistent with numerous other theories of institutional change. At the same time, we observe patterns of redistribution in subsequent years that are inconsistent with the commitment mechanism central to the Acemoglu-Robinson model. Building on these results, we discuss possible directions for future theoretical work.
A new genus and species of megalonychid sloth, Zacatzontli tecolotlanensis n. gen. n. sp., is described from the late Hemphillian of Jalisco, Mexico. Comparison and analysis of the type specimen, a mandible, with other megalonychid sloths shows a closer relationship to South American taxa than those from North America or the Caribbean. This suggests that during the early stages of the Great American Biotic Interchange there were two separate dispersal events of megalonychid sloths—an earlier one represented by Pliometanastes and the later one by Zacatzontli n. gen. While the morphology of the spout of Zacatzontli more closely resembles that of Megalonyx, based on the current record, Zacatzontli does does not enter North America until after the evolution of Megalonyx from Pliometanastes. The role of the northern neotropics in South America as a staging area for South American taxa that entered North America is discussed.
This work introduces for the first time the concept of using sinkholes in fluvial valleys as recorders of past floods. The notion is illustrated through the investigation of a complex sinkhole located in a broad floodplain underlain by salt-bearing Cenozoic evaporites. This active sinkhole comprises a large subsidence depression affecting the floodplain and the edge of a terrace, and a nested collapse sinkhole that used to host a sinkhole pond. A borehole drilled in the buried sinkhole pond revealed an ~7.8-m-thick fill that records around 2700 yr of clayey lacustrine deposition interrupted by three types of detrital facies. Two thick pebble gravel beds have been attributed to major high-competence floods: a paleoflood that occurred in Visigothic times (1537–1311 cal yr BP) and the 1961 Great Ebro River Flood, which is the largest event of the instrumental record. A trench dug in the portion of the terrace affected by subsidence exposed a mid-Holocene slack-water paleoflood deposit. The disadvantages and advantages of sinkholes as archives of past flood histories are discussed.
This study used proton magnetic resonance spectroscopy (1H MRS) to evaluate neurochemistry of the frontal cortex in adolescents with symptoms of sleep and depression.
19 non-medicated adolescent boys (mean age 16.0 y; n = 9 clinical cases with depression/sleep symptoms and n = 10 healthy controls) underwent 1H MRS at 3 T. MR spectra were acquired from the anterior cingulate cortex (ACC), the dorsolateral prefrontal cortex, and frontal white matter. Concentrations of N-acetyl aspartate, total creatine, choline-containing compounds, total glutamine plus glutamate, and myo-inositol (mI) were compared between the two subgroups and correlated with sleep and clinical measures in the total sample. Sleep was assessed with self-report questionnaires and ambulatory polysomnography recordings.
Concentrations of mI were lower in both frontal cortical regions among the depressed adolescents as compared to healthy controls. No statistically significant differences in other metabolite concentrations were observed between the subgroups. Frontal cortex mI concentrations correlated negatively with depression severity, subjective daytime sleepiness, insomnia symptoms, and the level of anxiety, and positively with total sleep time and overall psychosocial functioning. The correlations between mI in the ACC and total sleep time as well as daytime sleepiness remained statistically significant when depression severity was controlled in the analyses.
Lower frontal cortex mI may indicate a disturbed second messenger system. Frontal cortical mI may thus be linked to the pathophysiology of depression and concomitant sleep symptoms among maturing adolescents. Short sleep and daytime sleepiness may be associated with frontal cortex mI independently from depression.
Disclosure of interest
The authors have not supplied their declaration of competing interest.
The continuous interest in the synthesis and properties study of materials has permitted the development of semiconductor oxides. Zinc oxide (ZnO) with hexagonal wurzite structure is a wide band gap n-type semiconductor and interesting material over a wide range. Chemically sprayed aluminium-doped zinc oxide thin films (ZnO:Al) were deposited on soda-lime glass substrates starting from zinc pentanedionate and aluminium pentanedionate. The influence of both the dopant concentration in the starting solution and the substrate temperature on the composition, morphology, and transport properties of the ZnO:Al thin films were studied. The structure of all the ZnO:Al thin films was polycrystalline, and variation in the preferential growth with the aluminium content in the solution was observed: from an initial (002) growth in films with low Al content, switching to a predominance of (101) planes for heavily dopant regime. The crystallite size was found to decrease with doping concentration and range from 33 to 20 nm. First-order Raman scattering from ZnO:Al, all having the wurtzite structure . The assignments of the E2 mode in ZnO:Al differ from previous investigations. The film composition and the dopant concentration were determined by Auger Electron Spectroscopy (AES); these results showed that the films are almost stoichiometric ZnO. The optimum deposition conditions leading to conductive and transparent ZnO:Al thin films were also found. In this way a resistivity of 0.03 Ω-cm with a (002) preferential growth, were obtained in optimized ZnO:Al thin films.
In the present investigation, AA7075-T6 alloys and AZ31B-H24 were joined by the FSW process using the following range of parameters: rotational speed between 200 and 800 rpm, welding speed from 30 to 60 mm/min and a tilt angle from 1° to 3°. In some cases, a tool offset of 1 mm was used into Mg-based alloy. The experimental results show that sound and good joints can be obtained by positioning the tool in the middle of the joint-line using a rotational speed of 200 rpm, a welding speed of 30 mm/min and a tool tilt angle of 1°. The hardness and ultimate tensile strength in the stir zone were 122 Hv and 61.35 MPa, respectively. Also, it is important to mention that the Al3Mg2 and Al12Mg17 intermetallics compounds were observed in the this zone besides some defects like cavities and tunnel.
Electrochemical Impedance Spectroscopy (EIS), is a confirmed tool for investigation of electrode/electrolyte interfaces and surface-modified electrodes. In the present work, we apply this approaching way to obtain a deeper insight into the electrochemical oxidation mechanism of the glucose in alkaline media. We studied the EIS response of gold nanoparticles embedded in carbon paste and use it as an electrode for the electro-oxidation of glucose. The results were compared with those of a polycrystalline gold electrode. In order to determine the polarization potentials for EIS tests, cyclic voltammetry is first conducted in 0.3 M KOH with 10 mM glucose, recorded at a scan rate of 1 mVs-1. Three polarization potentials were chosen, corresponding to: the open circuit potential (OCP), glucose oxidation and gold oxide formation respectively.