Dairy farmers’ willingness to adopt cleaner production practices for water conservation: A discrete choice experiment in Mejia, Ecuador

Worldwide, farming practices directly impact the quality and quantity of both underground and surface water resources. In Mejia, the leading milk-producing region of Ecuador, the adoption rate of conservation practices among farmers is low despite price incentives established by the Agricultural Ministry. Our discrete choice experiment documents stated preferences for water conservation practices of Mejia’s dairy farmers by facing respondents to alternatives described in terms of water-efficient technologies, management of manure and solid waste, and training to resolve conflicts over water use. Estimates derived from our preferred random parameter logit specification imply that the average willingness to pay (WTP) for a solid rain irrigation system is US$147 ha-1; and US$212 ha-1 for training to resolve conflicts. In addition, we report heterogeneity in WTP estimates. These findings can assist in the resolution of current issues in Mejia, including inefficient water irrigation and weak water governance system. Based on our results and the context of our study area, we suggest, first, the adoption of a cost-sharing scheme (given that the WTP for these practices does not cover their implementation cost), and second, the participation of academic institutions to help these water users resolve conflicts, establish their own rules, and improve water governance

The role of competition and herbivory in biotic resistance against invaders: a synergistic effect

Invasive species pose a major threat to global diversity, and once they are well established their eradication typically becomes unfeasible. However, certain natural mechanisms can increase the resistance of native communities to invaders and can be used to guide effective management policies. Both competition and herbivory have been identified as potential biotic resistance mechanisms that can limit plant invasiveness, but it is still under debate to what extent they might be effective against well-established invaders. Surprisingly, whereas biotic mechanisms are known to interact strongly, most studies to date have examined single biotic mechanisms separately, which likely influences our understanding of the strength and effectiveness of biotic resistance against invaders. Here we use long-term field data, benthic assemblage sampling, and exclusion experiments to assess the effect of native assemblage complexity and herbivory on the invasion dynamics of a successful invasive species, the alga Caulerpa cylindracea. A higher complexity of the native algal assemblage limited C. cylindracea invasion, probably through competition by canopy-forming and erect algae. Additionally, high herbivory pressure by the fish Sarpa salpa reduced C. cylindracea abundance by more than four times. However, long-term data of the invasion reflects that biotic resistance strength can vary across the invasion process and it is only where high assemblage complexity is concomitant with high herbivory pressure, that the most significant limitation is observed (synergistic effect). Overall, the findings reported in this study highlight that neglecting the interactions between biotic mechanisms during invasive processes and restricting the studied time scales may lead to underestimations of the true capacity of native assemblages to develop resistance to invaders.Versión del editor4,84

A Bridging bis-Allyl Titanium Complex: Mechanistic Insights into the Electronic Structure and Reactivity

Treatment of the dinuclear compound [{Ti(η5-C5Me5)Cl2}2(μ-O)] with allylmagnesium chloride provides the formation of the allyltitanium(III) derivative [{Ti(η5-C5Me5)(μ-C3H5)}2(μ-O)] (1), structurally identified by single-crystal X-ray analysis. Density functional theory (DFT) calculations confirm that the electronic structure of 1 is a singlet state, and the molecular orbital analysis, along with the short Ti −Ti distance, reveal the presence of a metal −metal single bond between the two Ti(III) centers. Complex 1 reacts rapidly with organic azides, RN3 (R = Ph, SiMe3), to yield the allyl μ-imido derivatives [{Ti(η5-C5Me5)(CH2CH=CH2)}2(μ-NR)(μ-O)] [R = Ph(2), SiMe3(3)] along with molecular nitrogen release. Reaction of 2 and 3 with H2 leads to the μ-imido propyl species [{Ti(η5-C5Me5)(CH2CH2CH3)}2(μ-NR)(μ-O)] [R = Ph(4), SiMe3(5)]. Theoretical calculations were used to gain insight into the hydrogenation mechanism of complex 3 and rationalize the lower reactivity of 2. Initially, the μ-imido bridging group in these complexes activates the H2 molecule via addition to the Ti −N bonds. Subsequently, the titanium hydride intermediates induce a change in hapticity of the allyl ligands, and the nucleophilic attack of the hydride to the allyl groups leads to metallacyclopropane intermediates. Finally, the proton transfer from the amido group to the metallacyclopropane moieties affords the propyl complexes 4 and 5.Ministerio de Ciencia, Innovación y Universidades Universidad de Alcalá Generalitat de Cataluny

Local-scale climatic refugia offer sanctuary for a habitat-forming species during a marine heatwave

En prens

Reductive Hydrogenation of Sulfido-Bridged Tantalum Alkyl Complexes: A Mechanistic Insight

Hydrogenolysis of a series of alkyl sulfido-bridged tantalum(IV) dinuclear complexes [Ta(?5-C5Me5)R(?-S)]2 [R = Me, nBu (1), Et, CH2SiMe3, C3H5, Ph, CH2Ph (2), p-MeC6H4CH2 (3)] has led quantitatively to the Ta(III) tetrametallic sulfide cluster [Ta(?5-C5Me5)(?3-S)]4 (4) along with the corresponding alkane. Mechanistic information for the formation of the unique low-valent tetrametallic compound 4 was gathered by hydrogenation of the phenyl-substituted precursor [Ta(?5-C5Me5)Ph(?- S)]2, which proceeds through a stepwise hydrogenation process, disclosing the formation of the intermediate tetranuclear hydride sulfide [Ta2(?5-C5Me5)2(H)Ph(?-S)(?3-S)]2 (5). Extending our studies toward tantalum alkyl precursors containing functional groups susceptible to hydrogenation, such as the allyl-and benzylsubstituted compounds [Ta(?5-C5Me5)(?3-C3H5)(?-S)]2 and [Ta(?5-C5Me5)(CH2Ph)(?-S)]2 (2), enables alternative reaction pathways en route to the formation of 4. In the former case, the dimetallic system undergoes selective hydrogenation of the unsaturated allyl moiety, forming the asymmetric complex [{Ta(?5-C5Me5)(?3-C3H5)}(?-S)2{Ta(?5-C5Me5)(C3H7)}] (6) with only one propyl fragment. Species 2, in addition to the hydrogenation of one benzyl fragment and concomitant toluene release, also undergoes partial hydrogenation and dearomatization of the phenyl ring on the vicinal benzyl unity to give a ?5-cyclohexadienyl complex [Ta2(?5-C5Me5)2(?-CH2C6H6)(?-S)2] (7). The mechanistic implications of the latter hydrogenation process are discussed by means of DFT calculationsComunidad de MadridUniversidad de AlcaláPrograma Estímulo a la Investigación de Jóvenes Investigadore

N=N Bond Cleavage by Tantalum Hydride Complexes: Mechanistic Insights and Reactivity.

A series of dinuclear tantalum(IV) hydrides [{TaCpRX2}2(mu-H)2] (CpR = eta5-C5Me5, eta5-C5H4SiMe3, eta5-C5HMe4; X = Cl, Br) show the ability to promote the N=N bond cleavage in their reactions with azobenzene and benzo[c]cinnoline in absence of reducing reagents. Both, characterization of intermediate species and DFT studies point to a mechanism in two stages, in which the Ta-Ta bond splitting is key for the reduction of the N=N bond and its complete scission.Consorcio Madroño - Universidad de Alcal

Galectina-3 circulante tras el trasplante cardiaco: dinámica a largo plazo y valor pronóstico

[Abstract] Introduction and objectives: Circulating galectin-3 (Gal-3) is elevated and significantly correlates with all-cause and cardiovascular mortality in patients with heart failure. However, the relationship between serum Gal-3 and heart transplant (HT) outcomes is unclear. The aim of this study was to describe the longitudinal trend and prognostic value of Gal-3 levels after HT. Methods: Banked serum samples were available from 122 HT recipients, collected before transplant and at 1, 3, 6, and 12 months posttransplant. Gal-3 levels in these serum samples were measured by enzyme immune assay. Multivariable Cox regression was performed to determine the prognostic value of 12-month posttransplant Gal-3 serum levels. The primary endpoint was the composite variable all-cause death or graft failure over long-term posttransplant follow-up. Results: Circulating Gal-3 concentration steadily decreased during the first year after HT (median values: pretransplant, 19.1 ng/mL; 1-year posttransplant, 14.6 ng/mL; P<.001). Circulating Gal-3 levels 1-year posttransplant were associated with an increased risk of all-cause death or graft failure (adjusted HR per 1 ng/mL, 1.04; 95%CI, 1.01-1.08; P=.008). The predictive accuracy of this biomarker was moderate: area under the ROC curve, 0.72 (95%CI, 0.60-0.82; P<.001). Conclusions: Circulating Gal-3 steadily decreased during the first year after HT. However, 1-year posttransplant Gal-3 serum levels that remained elevated were associated with increased long-term risk of death and graft failure.[Resumen] Introducción y objetivos. Los valores plasmáticos de galectina-3 (Gal-3) están elevados y se correlacionan con la mortalidad total y cardiovascular en pacientes con insuficiencia cardiaca, pero su correlación con el pronóstico tras el trasplante cardiaco (TxC) es desconocida. El objetivo fue describir la tendencia evolutiva y el valor pronóstico de este biomarcador tras el TxC. Métodos. Mediante enzimoinmunoensayo, se midieron las concentraciones plasmáticas de Gal-3 en muestras de suero de 122 receptores de TxC, antes y 1, 3, 6 y 12 meses después de este. Mediante regresión de Cox se analizó el valor pronóstico del valor plasmático de Gal-3 a los 12 meses del TxC. El objetivo primario del estudio fue la variable combinada muerte o disfunción del injerto. Resultados. Las concentraciones de Gal-3 disminuyeron progresivamente durante el primer año tras el TxC (medianas: pretrasplante, 19,1 ng/ml; 1 año postrasplante, 14,6 ng/ml; p < 0,001). Los valores de Gal-3 1 año tras el TxC se asociaron con mayor riesgo de muerte o disfunción del injerto (HR por 1 ng/ml: 1.04; IC95%: 1,01-1,08; p = 0,008). La capacidad predictiva del biomarcardor fue moderada: área bajo la curva ROC, 0,72 (IC95%: 0,60-0,82; p < 0,001). Conclusiones. Las concentraciones plasmáticas de Gal-3 disminuyeron progresivamente durante el primer año tras el TxC. Un valor plasmático elevado de Gal-3 1 año tras el TxC se correlacionó con un pronóstico adverso.Instituto de Salud Carlos III; PI12/0267

Clethra fimbriata hexanic extract triggers alteration in the energy metabolism in epimastigotes of Trypanosoma cruzi

Chagas disease (ChD), caused by Trypanosoma cruzi, is endemic in American countries and an estimated 8 million people worldwide are chronically infected. Currently, only two drugs are available for therapeutic use against T. cruzi and their use is controversial due to several disadvantages associated with side effects and low compliance with treatment. Therefore, there is a need to search for new tripanocidal agents. Natural products have been considered a potential innovative source of effective and selective agents for drug development to treat T. cruzi infection. Recently, our research group showed that hexanic extract from Clethra fimbriata (CFHEX) exhibits anti-parasitic activity against all stages of T. cruzi parasite, being apoptosis the main cell death mechanism in both epimastigotes and trypomastigotes stages. With the aim of deepening the understanding of the mechanisms of death induced by CFHEX, the metabolic alterations elicited after treatment using a multiplatform metabolomics analysis (RP/HILIC-LC-QTOF-MS and GC-QTOF-MS) were performed. A total of 154 altered compounds were found significant in the treated parasites corresponding to amino acids (Arginine, threonine, cysteine, methionine, glycine, valine, proline, isoleucine, alanine, leucine, glutamic acid, and serine), fatty acids (stearic acid), glycerophospholipids (phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine), sulfur compounds (trypanothione) and carboxylic acids (pyruvate and phosphoenolpyruvate). The most affected metabolic pathways were mainly related to energy metabolism, which was found to be decrease during the evaluated treatment time. Further, exogenous compounds of the triterpene type (betulinic, ursolic and pomolic acid) previously described in C. fimbriata were found inside the treated parasites. Our findings suggest that triterpene-type compounds may contribute to the activity of CFHEX by altering essential processes in the parasite