776 research outputs found
A Platinum molecular complex immobilised on the surface of graphene as active catalyst in alkyne hydrosilylation
Abstract
A platinum complex bearing a N‐heterocyclic carbene (NHC) ligand functionalised with a pyrene‐tag is immobilised onto the surface of reduced graphene oxide (rGO). The hybrid material composed of an organometallic complex and a graphene derivative is ready available in a single‐step process under mild reaction conditions. This methodology preserves the inherent properties of the active catalytic centre and the support. The platinum hybrid material is an efficient catalyst in hydrosilylation of alkynes and can be recycled and reused for ten runs without significant loss of activity due to its high stability. Interestingly, the catalytic properties of the platinum complex are enhanced after immobilisation onto graphene. The influence of graphene in hydrosilylation of alkynes is discussed
Improving Catalyst Activity in Hydrocarbon Functionalization by Remote Pyrene–Graphene Stacking
A copper complex bearing an N‐heterocyclic carbene ligand with a pyrene “tail” attached to the backbone has been prepared and supported on reduced graphene oxide (rGO). The free and supported copper materials have been employed as homogeneous and heterogeneous catalysts in the functionalization of hydrocarbons such as n‐hexane, cyclohexane, and benzene through incorporation of the CHCO2Et unit from ethyl diazoacetate. The graphene‐anchored complex displays higher reaction rates and induces higher yields than its soluble counterpart, features that can be rationalized in terms of a decrease in electron density at the metal center due to a remote net electronic flux from the supported copper complex to the graphene surface.The authors would like to thank the financial support of the
MINECO (CTQ2017-82893-C2-1-R and CTQ2015-69153-C2-2-
R), Junta de Andalucía (P12-FQM-1765) and Universitat Jaume I
(UJI-B2018-23). D. V-E thanks the MINECO for a grant
(FPU15/03011). The authors thank the ‘Servei Central
d’Instrumentació Científica (SCIC)’ of the Universitat Jaume I
Identifying past social-ecological thresholds to understand long-term temporal dynamics in Spain
A thorough understanding of long-term temporal social-ecological dynamics at the national scale helps to explain the current condition of a country’s ecosystems and to support environmental policies to tackle future sustainability challenges. We aimed to develop a methodological approach to understand past long-term (1960-2010) social-ecological dynamics in Spain. First, we developed a methodical framework that allowed us to explore complex social-ecological dynamics among biodiversity, ecosystem services, human well-being, drivers of change, and institutional responses. Second, we compiled 21 long-term, national-scale indicators and analyzed their temporal relationships through a redundancy analysis. Third, we used a Bayesian change point analysis to detect evidence of past social-ecological thresholds and historical time periods. Our results revealed that Spain has passed through four socialecological thresholds that define five different time periods of nature and society relationships. Finally, we discussed how the proposed methodological approach helps to reinterpret national-level ecosystem indicators through a new conceptual lens to develop a more systems-based way of understanding long-term social-ecological patterns and dynamicsThis work was supported by the Biodiversity Foundation (http://www.fundacion-biodiversidad.es/) of the Spanish Ministry of Agriculture, Food and Environment. Partial
financial support was also provided by the Ministry of Economy and Competitiveness of Spain (project CGL2014-53782-P: ECOGRADIENTES). The Spanish National Institute for
Agriculture and Food Research and Technology (INIA) funded Marina García-Llorente as part of the European Social Fund. Blanca González García-Mon participated in this article as a “la
Caixa” Banking Foundation scholar. The funders had no role in the study design, data collection and analysis, preparation of the report, or the decision to submit the study for publicatio
Safety Profile and Tolerability of Topical Phosphodiesterase 4 Inhibitors for the Treatment of Atopic Dermatitis: A Systematic Review and Meta-Analysis
Evaluate the safety profile and tolerability of topical phosphodiesterase 4 (PDE4) inhibitors versus vehicle as treatment for atopic dermatitis in published studies.A search was performed in Medline/PubMed, Web of Science, and Cochrane Library databases on September 27, 2021, by 1 evaluator, without restrictions on publication dates or languages. Terms such as atopic dermatitis, phosphodiesterase 4 inhibitors, calcineurin inhibitors, and randomized controlled trials were included. The database searches were carried out by 1 evaluator. The titles and abstracts were reviewed for the identification and evaluation of potentially eligible studies. Study selection was made by two reviewers, so there was no intra-examiner statistic at the study selection step. The full-text articles were reviewed to determine whether or not they would be included in the systematic review. Global analyses, which included studies with both unclear and low risk of bias and subanalyses of studies with a low risk of bias were performed.Out of 237 identified articles, 14 clinical trials were included in the meta-analysis. In global analyses of studies with low and unclear risk of bias, topical treatment with PDE4 inhibitors did not differ from vehicle treatment in global treatment emergent adverse events (relative risk?=?0.99; 95% CI, 0.87-1.14; P?=?0.94) or in serious emergent adverse events appearance (relative risk?=?0.92; 95% CI, 0.39-2.20; P?=?0.86). In subanalyses of studies with a low risk of bias, a reduced rate of atopic dermatitis exacerbation was observed in PDE4 inhibitors compared with the vehicle (relative risk?=?0.62; 95% CI, 0.39-0.98; P?=?0.04) and risk of pain at the application site was confirmed (relative risk?=?2.59; 95% CI, 1.27-5.28; P?=?0.01).PDE4 inhibitors did not show differences from vehicle treatment in treatment emergent adverse events or serious emergent adverse events incidence. In studies with low risk of bias, PDE4 inhibitors had a statistically significant risk of producing pain and reduced occurrence of atopic dermatitis exacerbation.© 2022 The Author(s)
Dual role of graphene as support of ligand-stabilized palladium nanoparticles and carbocatalyst for (de)hydrogenation of N-heterocycles
The hybrid material composed of palladium nanoparticles (PdNPs) functionalized with N-heterocyclic carbene ligands (NHCs) immobilized onto the surface of reduced graphene oxide (rGO) results in an efficient catalytic material towards hydrogenation and dehydrogenation of N-heterocycles. The rGO plays a dual role by acting as a carbocatalyst in acceptorless dehydrogenation of N-heterocycles and as a support for the palladium nanoparticles facilitating its interaction with molecular hydrogen turning this hybrid material into an effective hydrogenation catalyst. Hot filtration experiments support the heterogeneous nature of the process underlining the strong interaction of palladium nanoparticles with the graphene enabled by π-interactions of the ligand with the support. The mild conditions used in both transformations of this system without requiring any additives facilitates its potential application in hydrogen storage technologies in the form of liquid organic hydrogen carriers (LOHCs). At the same time, the hybrid material is a robust and efficient catalytic platform that can be recovered and reused up to eight runs in both transformations without significant deactivation. The use of a single solid catalysts that is recyclable in hydrogen conversion and reconversion through (de)hydrogenation of N-heterocycles paves the way for the development of efficient hydrogen storage materials
¿Cuánta carga asistencial suponen las dermatosispediátricas en la actividad ambulatoria en ladermatología espa˜nola? Resultados del muestreoaleatorio nacional DIADERM
Un total de 20.097 diagnósticos fueron efectuados en pacientes menores de18 a˜nos, lo que supone un 12% del total de los codificados en DIADERM. Las infecciones víri-cas, el acné y la dermatitis atópica fueron los diagnósticos más comunes (43,9% de todos losdiagnósticos). No se observaron diferencias estadísticamente significativas en la proporción dediagnósticos atendidos en las consultas monográficas frente a las generales, así como en losregistrados en el ámbito público frente al privado. Tampoco las hubo en los diagnósticos enfunción de la época de la encuesta (enero y mayo).Conclusiones: La atención a pacientes pediátricos por parte de dermatólogos en Espa˜na suponeuna proporción significativa de la actividad habitual. Estos datos nos permiten descubrir áreasde mejora en la comunicación y la formación de los pediatras de atención primaria, comola necesidad del refuerzo de actividades formativas dirigidas al mejor tratamiento de acné ylesiones pigmentadas (y manejo básico de la dermatoscopia) en este ámbito asistencial.SurveyAbstractBackground: Visits for skin conditions are very common in pediatric primary care, and many ofthe patients seen in outpatient dermatology clinics are children or adolescents. Little, however,has been published about the true prevalence of these visits or about their characteristics.Material and methods: Observational cross-sectional study of diagnoses made in outpatientdermatology clinics during 2 data-collection periods in the anonymous DIADERM National Ran-dom Survey of dermatologists across Spain. All entries with an International Classification ofDiseases, Tenth Revision code related to dermatology in the 2 periods (84 diagnoses) were collec-ted for patients younger than 18 years and classified into 14 categories to facilitate analysisand comparison.Results: In total, the search found 20 097 diagnoses made in patients younger than 18 years (12%of all coded diagnoses in the DIADERM database). Viral infections, acne, and atopic dermatitiswere the most common, accounting for 43.9% of all diagnoses. No significant differences wereobserved in the proportions of diagnoses in the respective caseloads of specialist vs. generaldermatology clinics or public vs. private clinics. Seasonal differences in diagnoses (January vs.May) were also nonsignificant.Conclusions: Pediatric care accounts for a significant proportion of the dermatologist’s caseloadin Spain. Our findings are useful for identifying opportunities for improving communication andtraining in pediatric primary care and for designing training focused on the optimal treatmentof acne and pigmented lesions (with instruction on basic dermoscopy use) in these settings.El estudio DIADERM fue promovido por la Fundación Piel Sanade la AEDV, que recibió ayuda económica de Novarti
A simple prescription for simulating and characterizing gravitational arcs
Simple models of gravitational arcs are crucial to simulate large samples of
these objects with full control of the input parameters. These models also
provide crude and automated estimates of the shape and structure of the arcs,
which are necessary when trying to detect and characterize these objects on
massive wide area imaging surveys. We here present and explore the ArcEllipse,
a simple prescription to create objects with shape similar to gravitational
arcs. We also present PaintArcs, which is a code that couples this geometrical
form with a brightness distribution and adds the resulting object to images.
Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to
images of real gravitational arcs. We validate this fitting technique using
simulated arcs and apply it to CFHTLS and HST images of tangential arcs around
clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a
S\'ersic profile for the source, recovers the total signal in real images
typically within 10%-30%. The ArcEllipse+S\'ersic models also automatically
recover visual estimates of length-to-width ratios of real arcs. Residual maps
between data and model images reveal the incidence of arc substructure. They
may thus be used as a diagnostic for arcs formed by the merging of multiple
images. The incidence of these substructures is the main factor preventing
ArcEllipse models from accurately describing real lensed systems.Comment: 12 pages, 11 figures, accepted for publication in A&
Peroxidase expression in a cereal cyst nematode (Heterodera avenae) resistant hexaploid wheat line.
The incompatible interaction between plant and pathogen is often determined by the hypersensitive reaction (HR). This response is associated with accumulation of reactive oxygen species (ROS), which results in adverse growth conditions for pathogens. Two major mechanisms involving either NADPH oxidases or peroxidases have been proposed for generation of ROS. Peroxidases (PER, EC 1.11.1.7), present in all land plants, are members of a large multigenic family with high number of isoforms involved in a broad range of physiological processes. PER genes, which are expressed in nematode feeding sites, have been identified in several plant species (Zacheo et al. 1997). A strong correlation between HR and PER activities at four and seven days post nematode infection, was detected in roots of wheat lines carrying Cre2, Cre5 (from Ae. ventricosa) or Cre7 (from Ae. triuncialis) Heterodera avenae resistance genes (Andrés et al. 2001; Montes et al. 2003, 2004). We have studied changes in root of peroxidase mRNAs levels after infection by H. avenae of a wheat/Ae. ven¬tricosa introgression line (H-93-8) carrying Cre2 (Delibes et al. 1993). We also report and classify the predicted protein sequences derived from complete peroxidase transcripts
Serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy
During the analysis of RR Lyrae stars discovered in the High cadence
Transient Survey (HiTS) taken with the Dark Energy Camera at the 4-m telescope
at Cerro Tololo Inter-American Observatory, we found a group of three very
distant, fundamental mode pulsator RR Lyrae (type ab). The location of these
stars agrees with them belonging to the Leo V ultra-faint satellite galaxy, for
which no variable stars have been reported to date. The heliocentric distance
derived for Leo V based on these stars is 173 +/- 5 kpc. The pulsational
properties (amplitudes and periods) of these stars locate them within the locus
of the Oosterhoff II group, similar to most other ultra-faint galaxies with
known RR Lyrae stars. This serendipitous discovery shows that distant RR Lyrae
stars may be used to search for unknown faint stellar systems in the outskirts
of the Milky Way.Comment: Accepted in ApJ Letter
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