Interfacial chemistry in the electrocatalytic hydrogenation of CO2 over C-Supported Cu-Based systems

Operando soft and hard X-ray spectroscopic techniques were used in combination with plane-wave density functional theory (DFT) simulations to rationalize the enhanced activities of Zn-containing Cu nanostructured electrocatalysts in the electrocatalytic CO2 hydrogenation reaction. We show that at a potential for CO2 hydrogenation, Zn is alloyed with Cu in the bulk of the nanoparticles with no metallic Zn segregated; at the interface, low reducible Cu(I)–O species are consumed. Additional spectroscopic features are observed, which are identified as various surface Cu(I) ligated species; these respond to the potential, revealing characteristic interfacial dynamics. Similar behavior was observed for the Fe–Cu system in its active state, confirming the general validity of this mechanism; however, the performance of this system deteriorates after successive applied cathodic potentials, as the hydrogen evolution reaction then becomes the main reaction pathway. In contrast to an active system, Cu(I)–O is now consumed at cathodic potentials and not reversibly reformed when the voltage is allowed to equilibrate at the open-circuit voltage; rather, only the oxidation to Cu(II) is observed. We show that the Cu–Zn system represents the optimal active ensembles with stabilized Cu(I)–O; DFT simulations rationalize this observation by indicating that Cu–Zn–O neighboring atoms are able to activate CO2, whereas Cu–Cu sites provide the supply of H atoms for the hydrogenation reaction. Our results demonstrate an electronic effect exerted by the heterometal, which depends on its intimate distribution within the Cu phase and confirms the general validity of these mechanistic insights for future electrocatalyst design strategies

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Water at surfaces and interfaces: From molecules to ice and bulk liquid

The structure and growth of water films on surfaces is reviewed, starting from single molecules to two-dimensional wetting layers, and liquid interfaces. This progression follows the increase in temperature and vapor pressure from a few degrees Kelvin in ultra-high vacuum, where Scanning Tunneling and Atomic Force Microscopies (STM and AFM) provide crystallographic information at the molecular level, to ambient conditions where surface sensitive spectroscopic techniques provide electronic structure information. We show how single molecules bind to metal and non-metal surfaces, their diffusion and aggregation. We examine how water molecules can be manipulated by the STM tip via excitation of vibrational and electronic modes, which trigger molecular diffusion and dissociation. We review also the adsorption and structure of water on non-metal substrates including mica, alkali halides, and others under ambient humid conditions. We finally discuss recent progress in the exploration of the molecular level structure of solid-liquid interfaces, which impact our fundamental understanding of corrosion and electrochemical processes

Knowledge, Attitudes, and Practices (KAP) About Antibiotic Use in Hemodialysis Patients with Chronic Kidney Disease and Their Household Contacts, Medellín-Colombia

Daniela Montoya-Urrego,1 Juan José Velasco-Castaño,1 Juan C Quintero Velez,1– 3 J Natalia Jiménez Quiceno1 1Grupo de Investigación en Microbiología Básica y Aplicada (MICROBA), Escuela de Microbiología, Universidad de Antioquia, Medellín, Colombia; 2Grupo de Investigación Ciencias Veterinarias Centauro, Facultad de Ciencias Agrarias, Universidad de Antioquia, Medellín, Colombia; 3Grupo de Epidemiología, Facultad Nacional de Salud Pública, Universidad de Antioquia, Medellín, ColombiaCorrespondence: J Natalia Jiménez Quiceno, Universidad de Antioquia, Escuela de Microbiología, Calle 67 No. 53-108, Medellín, Antioquia, 050010, Colombia, Tel +57 604 219 54 97 ; +574-219-5481, Email [email protected]: The lack of knowledge and the excessive and inappropriate use of antibiotics are some of the causes of bacterial resistance. Hemodialysis patients have a high consumption of antibiotics and are constantly cared by their household contacts. This population circulates between hospital and community and are a model to study knowledge regarding bacterial resistance and antibiotic use in these settings. This study describes the knowledge, attitudes and practices (KAP) about antibiotic use and bacterial resistance in hemodialysis patients and their household contacts in Medellín-Colombia.Patients and Methods: A cross-sectional descriptive study was conducted on hemodialysis patients from a renal unit associated with a hospital in Medellín-Colombia, and their household contacts between May 2019 and March 2020. A KAP instrument was applied to participants during home visits. The KAP regarding antibiotic use were characterized, and a content analysis of open questions was made.Results: A total of 35 hemodialysis patients and 95 of their household contacts were included. Of participants, 83.1% (108/130) did not correctly identify the situations in which antibiotics should be used. Likewise, a gap in knowledge about antibacterial resistance was evidenced thanks to the emerging categories in content analysis. Regarding attitudes, 36.9% (48/130) of the participants discontinued antibiotic treatment when they felt better. Additionally, 43.8% (57/130) agree to keep antibiotics in their home. Finally, it was found that it is usual for pharmacists and family members to recommend or sell antibiotics without prescription; likewise, pharmacies were the most popular place to acquire these medications.Conclusion: This study identified gaps in KAP regarding the use of antibiotics and bacterial resistance in hemodialysis patients and their household contacts. This allows focusing education strategies in this regard, in order to increase awareness about the correct use of antibiotics and the consequences of bacterial resistance and to improve prevention actions in this vulnerable population.Keywords: KAP, antibiotics, bacterial resistanc

Photoelektronenspektroskopie an der Graphen-Flüssigelektrolyt-Grenzfläche zur Bestimmung der elektronischen Struktur eines elektrochemisch abgeschiedenen Cobalt/Graphen-Elektrokatalysators

Elektrochemisch gewachsenes Cobalt auf Graphen weist außergewöhnliche Katalysatoreigenschaften für die Sauerstoffentwicklungsreaktion (OER) auf und bietet die Möglichkeit, die Morphologie und die chemischen Eigenschaften während der Abscheidung zu kontrollieren. Es gibt allerdings noch kein ausreichendes Verständnis der atomaren Struktur dieses Hybridmaterials. Um die elektronische Struktur von Co/Graphen aufzuklären, haben wir eine Durchflusszelle entwickelt, die durch eine Graphenmembran abgeschlossen wird und elektronische und chemische Informationen über die aktiven Oberflächen unter atmosphärischem Druck und in der Gegenwart von flüssigen Elektrolyten unter Verwendung von Röntgenphotoelektronenspektroskopie (XPS) liefert. Wir konnten zeigen, dass Cobalt an Graphen über Carbonyl-ähnliche Spezies bindet, d. h. Co(CO)_x , und so die Reduktion von Co³⁺ zu Co²⁺ fördert, das als aktives Zentrum des Katalysators vermutet wird