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New electrochemical ammonia (NH 3 ) synthesis technologies are of interest as a complementary route to the Haber–Bosch process for distributed fertilizer generation, and towards exploiting ammonia as a zero-carbon fuel produced via renewably sourced electricity 1 . Apropos of these goals is a surge of fundamental research targeting heterogeneous materials as electrocatalysts for the nitrogen reduction reaction (N 2 RR) 2 . These systems generally suffer from poor stability and NH 3 selectivity; the hydrogen evolution reaction (HER) outcompetes N 2 RR 3 . Molecular catalyst systems can be exquisitely tuned and offer an alternative strategy 4 , but progress has been thwarted by the same selectivity issue; HER dominates. Here we describe a tandem catalysis strategy that offers a solution to this puzzle. A molecular complex that can mediate an N 2 reduction cycle is partnered with a co-catalyst that interfaces the electrode and an acid to mediate proton-coupled electron transfer steps, facilitating N−H bond formation at a favourable applied potential (−1.2 V versus Fc +/0 ) and overall thermodynamic efficiency. Certain intermediates of the N 2 RR cycle would be otherwise unreactive via uncoupled electron transfer or proton transfer steps. Structurally diverse complexes of several metals (W, Mo, Os, Fe) also mediate N 2 RR electrocatalysis at the same potential in the presence of the mediator, pointing to the generality of this tandem approach. Using a molecular catalyst and a proton–electron transfer mediator in tandem delivers efficient electroreduction of nitrogen to ammonia at modest potentials, an approach that could be used to improve other important reactions.

\"\"A lavishly illustrated two-volume study of the Taos Society of Artists. Essays on the TSA and its founding plus scholarly biographical and art historical essays on twelve TSA artists with exemplary works of the artists studied\"-Provided by publisher\"-- Provided by publisher.

Asthma is a disease of reversible airflow obstruction characterised clinically by wheezing, shortness of breath, and coughing. Increases in airway type 2 cytokine activity, including interleukin-4 (IL-4), IL-5, and IL-13, are now established biological mechanisms in asthma. Inhaled corticosteroids have been the foundation for asthma treatment, in a large part because they decrease airway type 2 inflammation. However, inhaled or systemic corticosteroids are ineffective treatments in many patients with asthma and few treatment options exist for patients with steroid resistant asthma. Although mechanisms for corticosteroid refractory asthma are likely to be numerous, the development of a new class of biologic agents that target airway type 2 inflammation has provided a new model for treating some patients with corticosteroid refractory asthma. The objective of this Therapeutic paper is to summarise the new type 2 therapeutics, with an emphasis on the biological rationale and clinical efficacy of this new class of asthma therapeutics.

Catalysis of the reduction of nitrogen to ammonia under mild conditions by a tris(phosphine)borane-supported iron complex indicates that a single iron site may be capable of stabilizing the various N x H y intermediates generated during catalytic ammonia formation. In search of an easy fix for nitrogen Industrial nitrogen fixation is performed on a vast scale by the Haber–Bosch process, which uses a solid-state iron catalyst at very high temperatures and pressures. Synthetic chemists have searched for decades for small metal-containing complexes to catalyse the transformation of nitrogen into ammonia in less extreme conditions, taking their lead from the nitrogenases found in plants and bacteria. To that end Jonas Peters and colleagues describe a tris(phosphine)borane-supported iron complex that catalyses the reduction of nitrogen into ammonia under mild conditions with reasonable efficiency. This suggests that a single iron site is sufficient for mediating nitrogen fixation, in line with recent biochemical and spectroscopic data that point to iron rather than the molybdenum also present in the FeMo cofactor or nitrogenase as the site of nitrogen binding and activation. The reduction of nitrogen (N 2 ) to ammonia (NH 3 ) is a requisite transformation for life 1 . Although it is widely appreciated that the iron-rich cofactors of nitrogenase enzymes facilitate this transformation 2 , 3 , 4 , 5 , how they do so remains poorly understood. A central element of debate has been the exact site or sites of N 2 coordination and reduction 6 , 7 . In synthetic inorganic chemistry, an early emphasis was placed on molybdenum 8 because it was thought to be an essential element of nitrogenases 3 and because it had been established that well-defined molybdenum model complexes could mediate the stoichiometric conversion of N 2 to NH 3 (ref. 9 ). This chemical transformation can be performed in a catalytic fashion by two well-defined molecular systems that feature molybdenum centres 10 , 11 . However, it is now thought that iron is the only transition metal essential to all nitrogenases 3 , and recent biochemical and spectroscopic data have implicated iron instead of molybdenum as the site of N 2 binding in the FeMo-cofactor 12 . Here we describe a tris(phosphine)borane-supported iron complex that catalyses the reduction of N 2 to NH 3 under mild conditions, and in which more than 40 per cent of the proton and reducing equivalents are delivered to N 2 . Our results indicate that a single iron site may be capable of stabilizing the various N x H y intermediates generated during catalytic NH 3 formation. Geometric tunability at iron imparted by a flexible iron–boron interaction in our model system seems to be important for efficient catalysis 13 , 14 , 15 . We propose that the interstitial carbon atom recently assigned in the nitrogenase cofactor may have a similar role 16 , 17 , perhaps by enabling a single iron site to mediate the enzymatic catalysis through a flexible iron–carbon interaction 18 .

Leishmaniasis, caused by protozoan parasites of the Leishmania genus, represents an important health problem in many regions of the world. Lack of effective point-of-care (POC) diagnostic tests applicable in resources-limited endemic areas is a critical barrier to effective treatment and control of leishmaniasis. The development of the loop-mediated isothermal amplification (LAMP) assay has provided a new tool towards the development of a POC diagnostic test based on the amplification of pathogen DNA. LAMP does not require a thermocycler, is relatively inexpensive, and is simple to perform with high amplification sensitivity and specificity. In this review, we discuss the current technical developments, applications, diagnostic performance, challenges, and future of LAMP for molecular diagnosis and surveillance of Leishmania parasites. Studies employing the LAMP assay to diagnose human leishmaniasis have reported sensitivities of 80% to 100% and specificities of 94% to 100%. These observations suggest that LAMP offers a good molecular POC technique for the diagnosis of leishmaniasis and is also readily applicable to screening at-risk populations and vector sand flies for Leishmania infection in endemic areas.

Despite a well-developed and growing body of work in copper catalysis, the potential of copper to serve as a photocatalyst remains underexplored. Here we describe a photoinduced copper-catalyzed method for coupling readily available racemic tertiary alkyl chloride electrophiles with amines to generate fully substituted stereocenters with high enantioselectivity. The reaction proceeds at −40°C under excitation by a blue light-emitting diode and benefits from the use of a single, Earth-abundant transition metal acting as both the photocatalyst and the source of asymmetric induction. An enantioconvergent mechanism transforms the racemic starting material into a single product enantiomer.

In arid ecosystems, current-year precipitation often explains only a small proportion of annual aboveground net primary production (ANPP). We hypothesized that lags in the response of ecosystems to changes in water availability explain this low explanatory power, and that lags result from legacies from transitions from dry to wet years or the reverse. We explored five hypotheses regarding the magnitude of legacies, two possible mechanisms, and the differential effect of previous dry or wet years on the legacy magnitude. We used a three-year manipulative experiment with five levels of rainfall in the first two years (−80% and −50% reduced annual precipitation (PPT), ambient, +50% and +80% increased PPT), and reversed treatments in year 3. Legacies of previous two years, which were dry or wet, accounted for a large fraction (20%) of interannual variability in production on year 3. Legacies in ANPP were similar in absolute value for both types of precipitation transitions, and their magnitude was a function of the difference between previous and current-year precipitation. Tiller density accounted for 40% of legacy variability, while nitrogen and carry-over water availability showed no effect. Understanding responses to changes in interannual precipitation will assist in assessing ecosystem responses to climate change-induced increases in precipitation variability.