ABSTRACT
The key role of morphological defects (e.g., irregular steps and dislocations) on the selectivity of model Cu catalysts for the electrocatalytic reduction of CO2 (CO2RR) is illustrated here. Cu(111) single-crystal surfaces prepared under ultrahigh vacuum (UHV) conditions and presenting similar chemical and local microscopic surface features were found to display different product selectivity during the CO2RR. In particular, changes in selectivity from hydrogen-dominant to hydrocarbon-dominant product distributions were observed based on the number of CO2RR electrolysis pretreatment cycles performed prior to a subsequent UHV surface regeneration treatment, which lead to surfaces with seemingly identical chemical composition and local crystallographic structure. However, significant mesostructural changes were observed through a micron-scale microscopic analysis, including a higher density of irregular steps on the samples producing hydrocarbons. Thus, our findings highlight that step edges are key for C-C coupling in the CO2RR and that not only atomistic but also mesoscale characterization of electrocatalytic materials is needed in order to comprehend complex selectivity trends.
ABSTRACT
OBJECTIVE: To present the results after balloon eustachian tuboplasty (BET) in patients with obstructive Eustachian tube dysfunction (OETD) grouped up into: baro-challenge, chronic serous otitis media and adhaesive otitis media. METHODS: A retrospective study was carried out on patients who underwent BET surgery. As outcome measures, otoscopy, tympanometry, Eustachian tube dysfunction questionnaire-7 (ETDQ-7) and ability to perform the Valsalva manoeuvre were recorded at baseline and at 3, 12 and 24 months after BET. A p value of 0.05 was used to indicate a statistically significant difference for all statistical tests. RESULTS: Three hundred and nineteen ears (248 patients) were included with a 3-month follow-up, 272 ears had a 12-month follow-up, and 171 ears had 24-month follow-up. Globally, a statistical significance improvement in all groups in all outcome measures was found. According to BET indication, in the baro-challenge group, there was no improvement in otoscopy, but ETDQ-7, Valsalva manoeuvre and tympanogram improved significantly. In the chronic serous otitis media group, otoscopy, ETDQ-7 and Valsalva manoeuvre were significantly improved in all the three timelines, including the avoidance of a new transtympanic tube after the BET in over 80% of cases. In the adhaesive otitis media group, Valsalva manoeuvre improved significantly, ETDQ-7 decreased and tympanogram improved but not significantly. Few mild complications were reported. CONCLUSIONS: BET is an effective method for the treatment of OETD in all etiologic groups. The greatest benefit was observed in patients with baro-challenge. A long-term follow-up is recommended since the benefit seems to increase over time.
Subject(s)
Ear Diseases , Eustachian Tube , Otitis Media with Effusion , Otitis Media , Humans , Otitis Media with Effusion/surgery , Treatment Outcome , Eustachian Tube/surgery , Retrospective Studies , Cohort Studies , Dilatation/methods , Acoustic Impedance Tests , Ear Diseases/surgery , Chronic DiseaseABSTRACT
Tuning the properties of oxide surfaces through the adsorption of designed ligands is highly desirable for several applications, such as catalysis. N-Heterocyclic carbenes (NHCs) have been successfully employed as ligands for the modification of metallic surfaces. On the other hand, their potential as modifiers of ubiquitous oxide surfaces still needs to be developed. Here we show that a model NHC binds covalently to a copper oxide surface under UHV conditions. In particular, we report the first example of a covalent bond between NHCs and oxygen atoms from the oxide layer. This study demonstrates that NHC can also act as a strong anchor on oxide surfaces.
ABSTRACT
N-Heterocyclic carbenes (NHCs) have superior properties as building blocks of self-assembled monolayers (SAMs). Understanding the influence of the substrate in the molecular arrangement is a fundamental step before employing these ligands in technological applications. Herein, we study the molecular arrangement of a model NHC on Cu(100) and Cu(111). While mostly disordered phases appear on Cu(100), on Cu(111) well-defined structures are formed, evolving from magic-number islands to molecular ribbons with coverage. This work presents the first example of magic-number islands formed by NHC assemblies on flat surfaces. Diffusion and commensurability are key factors explaining the observed arrangements. These results shed light on the molecule-substrate interaction and open the possibility of tuning nanopatterned structures based on NHC assemblies.
ABSTRACT
Electrocatalyst surfaces prepared under ultrahigh vacuum (UHV) conditions can create model surfaces to better connect theoretical calculations with experimental studies. The development of a single crystal sample holder and inert electrochemical cells prepared with modularity and chemical stability in mind would allow for expensive single crystals to be reused indefinitely in both UHV and electrochemical settings. This sample holder shows reproducible surface preparations for single crystal samples and consistent electrochemical experiments without the introduction of impurities into the surface. The presented setup has been used as a critical piece for the characterization of Cu(111) surfaces under CO2 electrochemical reduction reaction conditions as a test case.
ABSTRACT
The influence of the crystallographic orientation on surface segregation and alloy formation in model PdCu methanol synthesis catalysts was investigated in situ using near-ambient pressure X-ray photoelectron spectroscopy under CO2 hydrogenation conditions. Combined with scanning tunneling microscopy and density functional theory calculations, the study showed that submonolayers of Pd undergo spontaneous alloy formation on Cu(110) and Cu(100) surfaces in vacuum, whereas they do not form an alloy on Cu(111). Upon heating in H2, inward diffusion of Pd into the Cu lattice is favored, facilitating alloying on all Cu surfaces. Under CO2 hydrogenation reaction conditions, the alloying trend becomes stronger, promoted by the reaction intermediate HCOO*, especially on Pd/Cu(110). This work demonstrates that surface alloying may be a key factor in the enhancement of the catalytic activity of PdCu catalysts as compared to their monometallic counterparts. Furthermore, it sheds light on the hydrogen activation mechanism during catalytic hydrogenation on copper-based catalysts.
ABSTRACT
Regional climate modeling bridges the gap between the coarse resolution of current global climate models and the regional-to-local scales, where the impacts of climate change are of primary interest. Here, we present a review of the added value of the regional climate modeling approach within the scope of paleoclimate research and discuss the current major challenges and perspectives. Two time periods serve as an example: the Holocene, including the Last Millennium, and the Last Glacial Maximum. Reviewing the existing literature reveals the benefits of regional paleo climate modeling, particularly over areas with complex terrain. However, this depends largely on the variable of interest, as the added value of regional modeling arises from a more realistic representation of physical processes and climate feedbacks compared to global climate models, and this affects different climate variables in various ways. In particular, hydrological processes have been shown to be better represented in regional models, and they can deliver more realistic meteorological data to drive ice sheet and glacier modeling. Thus, regional climate models provide a clear benefit to answer fundamental paleoclimate research questions and may be key to advance a meaningful joint interpretation of climate model and proxy data.
Subject(s)
Climate Change , Ecosystem , Models, Theoretical , TemperatureABSTRACT
No disponible
Subject(s)
Humans , Myocardial Infarction/rehabilitation , Primary Health Care/trends , Professional-Family Relations , Hospital-Patient RelationsABSTRACT
Un aspecto de pobre manejo en la rehabilitación cardiovascular de pacientes con infarto agudo del miocardio es el comportamiento sexual después del evento coronario, influído tal vez por prejuicios y tabués tanto en los pacientes como en el personal sanitario encargado de esta rehabilitación.
Subject(s)
Humans , Sexual Behavior/psychology , Myocardial Infarction/rehabilitationABSTRACT
Un aspecto de pobre manejo en la rehabilitación cardiovascular de pacientes con infarto agudo del miocardio es el comportamiento sexual después del evento coronario, influído tal vez por prejuicios y tabués tanto en los pacientes como en el personal sanitario encargado de esta rehabilitación (AU)
Subject(s)
Humans , Myocardial Infarction/rehabilitation , Sexual Behavior/psychologyABSTRACT
Presentamos el caso de una niña de 18 meses que fue atendida en la sala de nutrición delHospital Escuela que se presentó con un cuadro de infección respiratoria, desnutrición proteico-calorica, anemia, fiebre y visceromegalia. Se demostró en la médula ósea la presencia de amastigotos de leishmania y levaduras de histoplasma, que fueron confirmados con cultivo. La coinfección por estos organismos es un evento infrecuente aún en áreas endémicas para ambos patógenos
Subject(s)
Humans , Female , Infant , Histoplasmosis/complications , Leishmaniasis, Visceral/complications , Histoplasma , Leishmania donovaniABSTRACT
Se presenta el caso de una pre-escolar, hondureña, con desnutrición calórica protéica grado III, de causa secundaria, con múltiples infecciones bacterianas, virales y micóticas de repetición, que al ser investigada por inmunocompromiso se diagnostica síndrome de inmunodeficiencia adquirida. Debe tenerse presente éste diagnóstico en el estudio de pacientes desnutridos por causa secundaria con infecciones a repetición (aU)
Subject(s)
Child, Preschool , Humans , Protein-Energy Malnutrition , Acquired Immunodeficiency Syndrome/complicationsABSTRACT
Se presenta el caso de una pre-escolar, hondureña, con desnutrición calórica protéica grado III, de causa secundaria, con múltiples infecciones bacterianas, virales y micóticas de repetición, que al ser investigada por inmunocompromiso se diagnostica Síndrome de Inmunodeficiencia Adquirida. Debe tenerse presente este diagnóstico en el estudio de pacientes desnutridos por causa secundaria con infecciones a repetición
