MXenes as Heterogeneous Thermal Catalysts: Regioselective Anti-Markovnikov Hydroamination of Terminal Alkynes with 10 h Turnover Frequencies.

Due to their conductive properties and optoelectronic tunability, MXenes have revolutionized the area of electrocatalysis and active materials in supercapacitors. In comparison, there are only a few reports on MXenes as thermal catalysts for general organic reactions. Herein, the unprecedented catalytic activity of TiC MXene for the hydroamination of alkynes is reported, overcoming the limitations of poor activity, lack of selectivity, and stability, which are generally encountered in the solid catalysts known so far.

Frequency of in dogs from the municipality of Veracruz, Mexico.

Infectious canine cyclic thrombocytopenia or canine anaplasmosis is an infectious disease caused by . In Mexico, cases of human infection have been reported. The present cross-sectional study aimed to determine the frequency of infection in the municipality of Veracruz, Mexico, by nested polymerase chain reaction method.

Molten Salt Derived MXenes: Synthesis and Applications.

About one decade after the first report on MXenes, these 2D early transition metal carbides or nitrides have become among the best-performing materials in electrode applications related to electrical energy storage devices and power-to-fuels conversion. MXenes are obtained by a top-down approach starting from the appropriate 3D MAX phase that undergoes etching of the A-site metal. Initial etching procedures are based on the use of concentrated HF or the in situ generation of this highly corrosive and poisonous reagent.

Opportunities of MXenes in Heterogeneous Catalysis: VC as Aerobic Oxidation Catalyst.

MXenes are two-dimensional nanomaterials having alternating sheets of one atom-thick early transition metal layer and one atom-thick carbide or nitride layer. The external surface contains termination groups, whose nature depends on the etching agent used in the preparation procedure from the MAX phase. The present concept proposes that, due to their composition, the metal-surface termination groups make MXenes particularly suited as heterogeneous catalysts for some reactions.

Nanometric Cu-ZnO Particles Supported on N-Doped Graphitic Carbon as Catalysts for the Selective CO Hydrogenation to Methanol.

The quest for efficient catalysts based on abundant elements that can promote the selective CO hydrogenation to green methanol still continues. Most of the reported catalysts are based on Cu/ZnO supported in inorganic oxides, with not much progress with respect to the benchmark Cu/ZnO/AlO catalyst. The use of carbon supports for Cu/ZnO particles is much less explored in spite of the favorable strong metal support interaction that these doped carbons can establish.

Selective Gas-Phase Hydrogenation of CO to Methanol Catalysed by Metal-Organic Frameworks.

Large scale production of green CH OH obtained from CO and green H is a highly wanted process due to the role of CH OH as H /energy carrier and for producing chemicals. Starting with a short summary of the advantages of metal-organic frameworks (MOFs) as catalysts in liquid-phase reactions, the present article highlights the opportunities that MOFs may offer also for some gas-phase reactions, particularly for the selective CO hydrogenation to CH OH. It is commented that there is a temperature compatibility window that combines the thermal stability of some MOFs with the temperature required in the CO hydrogenation to CH OH that frequently ranges from 250 to 300 °C.

Dissipative optomechanics in high-frequency nanomechanical resonators.

The coherent transduction of information between microwave and optical domains is a fundamental building block for future quantum networks. A promising way to bridge these widely different frequencies is using high-frequency nanomechanical resonators interacting with low-loss optical modes. State-of-the-art optomechanical devices rely on purely dispersive interactions that are enhanced by a large photon population in the cavity.

Climate forcing on estuarine zooplanktonic production.

Estuaries are among the most valuable aquatic systems in the world and resolving how there are impacted by climate change is fundamental to their management under global change scenarios. In this study, a ten-year time series (2003-2013) of zooplankton in an estuarine area (Mondego estuary, Portugal) is used to determine the impact of climate variability on estuarine zooplanktonic secondary production. For that, a trend analysis of seasonal zooplankton production was applied and their link with large-scale, regional, and local environment was tested by Distance-based multivariate multiple regression (DistLM).

Short and long-term temperature variations drive recruitment variability in marine and estuarine juvenile fishes.

Understanding the long-term effects of climatic factors on key species' recruitment is crucial to species management and conservation. Here, we analysed the recruitment variability of key species (Dicentrarchus labrax, Platichthys flesus, Solea solea, Pomatoschistus microps and Pomatoschistus minutus) in an estuary between 2003 and 2019, and related it with the prevailing local and large-scale environmental factors. Using a dynamic factor analysis (DFA), juvenile abundance data were grouped into three common trends linked to different habitat uses and life cycle characteristics, with significant effect of temperature-related variables on fish recruitment: Sea surface temperature and the Atlantic Multidecadal Oscillation.

Slash and burn management and permanent or rotation agroforestry systems: A comparative study for C sequestration by century model simulation.

Understanding the effects of agroforestry systems (AFs) on soil organic carbon (SOC) requires long-term experiments, but scenarios simulations can anticipate the potential of these systems to sequester or lose carbon (C). This study aimed to simulate the SOC dynamics in slash and burn management (BURN) and AFs using the Century model. Data from a long-term experiment implemented in the Brazilian semiarid region were used to simulate SOC dynamics under BURN and AFs situations, and the natural vegetation (NV) "Caatinga" as a reference.

Interannual variability in early life phenology is driven by climate and oceanic processes in two NE Atlantic flatfishes.

Early life phenology is a crucial factor for population dynamics in a climate change scenario. As such, understanding how the early life cycle of marine fishes is influenced by key oceanic and climate drivers is of chief importance for sustainable fisheries. This study documents interannual changes in early life phenology of two commercial flatfishes: European flounder (Platichthys flesus) and common sole (Solea solea) from 2010 to 2015 based on otolith microstructure.

Green, HF-Free Synthesis of MXene Quantum Dots and their Photocatalytic Activity for Hydrogen Evolution.

A general methodology to prepare MXene quantum dots (MxQDs) with yields over 20% by liquid-phase laser ablation of the MAX phase is reported. Mechanical and thermal shock by 532 nm laser pulses (7 ns fwhp, 50 mJ × pulse , 1 Hz pulse frequency) produces MAX etching and exfoliation to form MXene QDs, avoiding the use of HF. The process can be followed by absorption and emission spectroscopy and by dynamic laser scattering and it appears to be general, being applied to Ti AlC , Ti AlC, Nb AlC, and V AlC MAX phases.

Promotional Effects on the Catalytic Activity of Co-Fe Alloy Supported on Graphitic Carbon for CO Hydrogenation.

Starting from the reported activity of Co-Fe nanoparticles wrapped onto graphitic carbon (Co-Fe@C) as CO hydrogenation catalysts, the present article studies the influence of a series of metallic (Pd, Ce, Ca, Ca, and Ce) and non-metallic (S in various percentages and S and alkali metals) elements as Co-Fe@C promoters. Pd at 0.5 wt % somewhat enhances CO conversion and CH selectivity, probably due to H activation and spillover on Co-Fe.

All-carbon microporous graphitic photocatalyst-promoted reduction of CO to CO in the absence of metals or dopant elements.

Microporous graphitic carbon (mp-C) derived from the pyrolysis of α-, β-, and γ-cyclodextrins exhibited photocatalytic activity in CO-saturated acetonitrile-water upon irradiation with UV-Vis light and in the presence of triethanolamine, forming H (19 μmol h) and CO (23 μmol h) accompanied by a lesser proportion of CH (4 μmol h). The most efficient was the mp-C material derived from α-cyclodextrin (mp-C) and having a pore dimension of 0.68 nm.

Synergistic effect of Cu and Fe small nanoparticles supported on porous N-doped graphitic framework for selective electrochemical CO reduction at low overpotential.

Electrochemical CO reduction is an appealing approach to diminish CO emissions, while obtaining valuable chemicals and fuels from renewable electricity. However, efficient electrocatalysts exhibiting high selectivity and low operating potentials are still needed. Herein it is reported that Cu and Fe nanoparticles supported on porous N-doped graphitic carbon matrix are efficient and selective electrocatalysts for CO reduction to CO at low overpotentials.

High C-C selectivity in CO hydrogenation by particle size control of Co-Fe alloy nanoparticles wrapped on N-doped graphitic carbon.

A catalyst based on first-row Fe and Co with a record of 51% selectivity to C-C hydrocarbons at 36% CO conversion is disclosed. The factors responsible for the C selectivity are a narrow Co-Fe particle size distribution of about 10 nm and embedment in N-doped graphitic matrix. These hydrogenation catalysts convert CO into C-C hydrocarbons, including ethane, propane, butane, ethylene and propylene together with methane, CO.

Tridimensional N, P-Codoped Carbon Sponges as Highly Selective Catalysts for Aerobic Oxidative Coupling of Benzylamine.

Two tridimensional N-doped porous carbon sponges (3DC-X) have been prepared by using cetyltrimethylammonium chloride (CTAC) and cetyltrimethylammonium bromide (CTAB) as soft templates and alginate to replicate the liquid crystals formed by CTA in water. Alginate is a filmogenic polysaccharide of natural origin having the ability to form nanometric defectless films around objects. Subsequent pyrolysis at 900 °C under an Ar flow of the resulting CTA-polysaccharide assemblies result in 3DC-1 and 3DC-2, with the N percentages of 0.

Two-Loop Four-Fermion Scattering Amplitude in QED.

We present the first fully analytic evaluation of the transition amplitude for the scattering of a massless into a massive pair of fermions at the two-loop level in quantum electrodynamics. Our result is an essential ingredient for the determination of the electromagnetic coupling within scattering reactions, beyond the currently known accuracy, which has a crucial impact on the evaluation of the anomalous magnetic moment of the muon. It will allow, in particular, for a precise determination of the leading hadronic contribution to the (g-2)_{μ} in the MUonE experiment at CERN, and therefore can be used to shed light on the current discrepancy between the standard model prediction and the experimental measurement for this important physical observable.

Influences of Climate Change and Variability on Estuarine Ecosystems: An Impact Study in Selected European, South American and Asian Countries.

It is well-known that climate change significantly impacts ecosystems (at the macro-level) and individual species (at the micro-level). Among the former, estuaries are the most vulnerable and affected ecosystems. However, despite the strong relations between climate change and estuaries, there is a gap in the literature regarding international studies across different regions investigating the impacts of climate change and variability on estuaries in different geographical zones.

Band Engineering of Semiconducting Microporous Graphitic Carbons by Phosphorous Doping: Enhancing of Photocatalytic Overall Water Splitting.

Carbon-based solar photocatalysts for overall water splitting could provide H as an energy vector in a clean and sustainable way. Band engineering to align energy levels can be achieved, among other ways, by doping. Herein, it is shown that phosphorous doping of microporous graphitic carbons derived from pyrolysis of α-, β-, and γ-cyclodextrin increases the valence band edge energy of the material, and the energy value of the conduction band decreases with the P content.

Fe clusters embedded on N-doped graphene as a photothermal catalyst for selective CO hydrogenation.

In comparison with the Co analog, small Fe clusters incorporated in a graphene matrix exhibit a photo-assisted increase of 110% in reverse water gas shift CO hydrogenation under UV-Vis light irradiation. Available data indicate that the photo-assistance derives from light absorption by the N-doped graphene followed by charge recombination at the Fe clusters, increasing their local temperature.

Co-Fe Nanoparticles Wrapped on N-Doped Graphitic Carbons as Highly Selective CO Methanation Catalysts.

Pyrolysis of chitosan containing various loadings of Co and Fe renders Co-Fe alloy nanoparticles supported on N-doped graphitic carbon. Transmission electron microscopy (TEM) images show that the surface of Co-Fe NPs is partially covered by three or four graphene layers. These Co-Fe@(N)C samples catalyze the Sabatier CO hydrogenation, increasing the activity and CH selectivity with the reaction temperature in the range of 300-500 °C.