π‐Bridge Substitution in DASAs: The Subtle Equilibrium between Photochemical Improvements and Thermal Control

Donor-acceptor Stenhouse adducts (DASAs) are playing an outstanding role as innovative and versatile photoswitches. Until now, all the efforts have been spent on modifying the donor and acceptor moieties to modulate the absorption energy and improve the cyclization and reversion kinetics. However, there is a strong dependence on specific structural modifications and a lack of predictive behavior, mostly owing to the complex photoswitching mechanism. Here, by means of a combined experimental and theoretical study, the effect of chemical modification of the pi-bridge linking the donor and acceptor moieties is systematically explored, revealing the significant impact on the absorption, photocyclization, and relative stability of the open form. In particular, a position along the pi-bridge is found to be the most suited to redshift the absorption while preserving the cyclization. However, thermal back-reaction to the initial isomer is blocked. These effects are explained in terms of an increased acceptor capability offered by the pi-bridge substituent that can be modulated. This strategy opens the path toward derivatives with infra-red absorption and a potential anchoring point for further functionalization

Aplicación de una nariz electrónica tipo QCM para la medida de aromas emitidos por manzanas cv. Fuji conservadas con diferentes tecnologías

La nariz electrónica (NE) “Libra Nose” se basa en una matriz de 8 sensores del tipo Microbalanzas de Cristal de Cuarzo. Estudios previos muestran que es posible utilizar una NE para hacer un seguimiento de la evolución de la calidad de fruta sometida a diferentes periodos de almacenamiento. En este trabajo se muestra que al analizar la emisión aromática de frutos de manzana cv.Fuji, con NE y cromatografía de gases, es posible por una lado detectar con la NE diferencias significativas en el espacio de cabeza generado por manzanas sometidas a diferentes tiempos de almacenamiento y periodos de vida en estantería, y por otro lado establecer para los frutos almacenados en condiciones de frío normal y atmósfera controlada estándar, una correlación positiva entre la respuesta de los sensores de la NE y la emisión de uno de los compuestos predominantes en el aroma de la variedad Fuji, el acetato de hexilo

Aplicación de una nariz electrónica para la medida de aromas emitidos por manzanas cv. Fuji conservadas con diferentes tecnologías

La nariz electrónica (NE) "Libra Nose" se basa en una matriz de 8sensores del tipo Micro balanzas de Cristal de Cuarzo. Estudios previos muestran que es posible utilizar una NE para hacer un seguimiento de la evolución de la calidad de fruta sometida a diferentes periodos de almacenamiento. En este trabajo se muestra que al analizar la emisión aromática de frutos de manzana cv. Fuji con una NE y un cromatógrafo de gases, es posible por una lado detectar con la NE diferencias significativas en el espacio de cabeza generado por manzanas sometidas a diferentes tiempos de almacenamiento y periodos de vida en estantería, y por otro lado establecer para los frutos almacenados en condiciones de frío normal y atmósfera controlada estándar, una correlación positiva entre la respuesta de los sensores de la NE y la emisión de uno de los compuestos predominantes en el aroma de la variedad Fuji, el acetato de hexílo

Use of a QCM electronic nose to evaluate the aromatic quality in apples

The “Libra Nose” electronic nose has eight Quartz Microbalance Sensors. When gas molecules are adsorbed onto the quartz crystal surface, the oscillation frequency changes in proportion to the amount of mass. The response of sensors depends on numerous factors that may be difficult to control, such as the temperature and the humidity of the carrier gas. All these factors cause changes in the selectivity of sensors which affect the reproducibility of measurements. In this paper additive and multiplicative corrections are proposed to be applied to the raw sensors´s signal in order to eliminate sources of variation. After these corrections, the sensors´ response gives useful information to distinguish between batches of apples with different ripeness stage

Increasing efficiency and reducing bias in the sampling of seed-dispersal interactions based on mist-netted birds

Efficient and unbiased sampling of ecological interactions is essential to our understanding of the functions they mediate. Seed dispersal by frugivorous birds is a key mutualism for plant regeneration and community dynamics. Mist-netting is one of the most widely used methods to sample avian seed dispersal through the identification of seeds in droppings of captured birds kept inside cloth bags. However, birds may drop seeds on the ground before being extracted from the net, leading to a fraction of missing information due to ineffective sampling. Worryingly, this fraction could be unevenly distributed across bird and plant species, leading to sampling biases. Here, we assess the effectiveness of using a 1-m wide mesh below mist nets to sample seeds dropped by entangled birds. We used data from birds mist-netted during one-year-round. We sampled nearly 50% of interaction events and 75% of dispersed seeds on the mesh band below the mist nets (i.e. lost information without this optimization). The proportion of seeds sampled on the mesh bands was not evenly distributed among bird species but strongly related to bird size, ranging from 57–63% in warblers to 84–94% in thrushes. Moreover, the proportion of seeds sampled on the mesh was negatively related to seed size, although this relationship was weaker. We also evaluated accumulation curves of species and pairwise interactions with increasing sampling effort, both with and without using the mesh bands. The number of seed species sampled increased by 21% when using the mesh bands and the number of pairwise interactions by 36%. Our findings provide strong evidence on how inefficient and biased traditional mist-netting can be for sampling community-wide seed–dispersal interactions. We thus urge the use of mesh bands in future studies to increase sampling effectiveness and avoid biases, which will ultimately improve our understanding of the seed dispersal function

Production of HlyA and ClyA haemolysins among quinolone-resistant Escherichia coli isolated from clinical samples

Most Escherichia coli resistant to quinolones are not haemolytic. The objective of this study was to determine the phylogroup, clonal relationship, mechanism of quinolone resistance and virulence factors in 70 haemolytic E. coli resistant to nalidixic acid. Sixty-six isolates contained the hlyA gene, belonged to phylogroup B2, and 61 of them presented low-level resistance to fluoroquinolones. Four isolates presented high-level resistance to fluoroquinolones, contained the clyA gene and were included in phylogroup D. One single isolate (phylogroup D, with low level resistance to fluoroquinolones) contained both cytotoxins.Supported by Ministerio de Economía y Competitividad, Instituto de Salud Carlos III, Madrid, Spain, co-financed by European Development Regional Fund “A way to achieve Europe” ERDF, Spanish Network for the Research in Infectious Diseases (REIPI RD12/0015). Alicia Márquez-López was supported by the REIPI and has been supported by a grant from the Instituto de Formación e Investigación Marqués de Valdecilla (IFIMAV), Santander, Spain. We want to thank Eduardo López for his review of English version of the manuscript.S

Familia, amigos y otras fuentes de información asociadas al inicio de las relaciones sexuales en adolescentes de El Salvador

Objetivo. El objetivo de este estudio es comprobar cómo influyen en el inicio de la actividad sexual de los jóvenes salvadoreños los mensajes que reciben sobre cuestiones de sexualidad, afectividad y ocio a través de la familia, los amigos y los medios de comunicación. Métodos. Estudio transversal a partir de una muestra representativa de 2 615 estudiantes (de 13 a 19 años) de El Salvador. Se utilizó un muestreo sistemático aleatorio para seleccionar 30 colegios. Se recogieron aspectos sociodemográficos, estilos de vida y fuentes de información sobre sexualidad y amor utilizadas por los jóvenes. Resultados. La edad media de los jóvenes fue de 15 años (DE = 1,8). En total 638 (24,4%) jóvenes afirmaron haber tenido relaciones sexuales. Los siguientes factores se asociaron con una mayor probabilidad de haber tenido relaciones sexuales: percibir que los hermanos (OR = 1,8, IC 95%: 1,2–2,7) o los amigos (OR = 1,7, IC 95%: 1,3–2,2) apoyan que se tengan relaciones sexuales. Como factores protectores se encontraron la supervisión de los padres (OR = 0,5, IC 95%: 0,4–0,7); recibir mensajes que apoyan la abstinencia por parte de amigos (OR = 0,7, IC 95%: 0,6–1,0) o hermanos (OR = 0,7, IC 95%: 0,5–0,8) y recibir mensajes favorables al matrimonio por parte de los padres (OR = 0,4, IC 95%: 0,3–0,6). Conclusiones. Los mensajes de la familia y amigos son factores que parecen influir en el inicio de las relaciones sexuales de los jóvenes. Los programas de promoción de la salud sexual en El Salvador deberían tener en cuenta estos factores

Improved graphene blisters by ultrahigh pressure sealing

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials and Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To acces final work see “Improved Graphene Blisters by Ultrahigh Pressure Sealing”, ACS Applied Materials and Interfaces 12.33 (2020): 37750-37756, 10.1021/acsami.0c09765Graphene is a very attractive material for nanomechanical devices and membrane applications. Graphene blisters based on silicon oxide microcavities are a simple but relevant example of nanoactuators. A drawback of this experimental setup is that gas leakage through the graphene-SiO2 interface contributes significantly to the total leak rate. Here, we study the diffusion of air from pressurized graphene drumheads on SiO2 microcavities and propose a straightforward method to improve the already strong adhesion between graphene and the underlying SiO2 substrate, resulting in reduced leak rates. This is carried out by applying controlled and localized ultrahigh pressure (>10 GPa) with an atomic force microscopy diamond tip. With this procedure, we are able to significantly approach the graphene layer to the SiO2 surface around the drumheads, thus enhancing the interaction between them, allowing us to better seal the graphene-SiO2 interface, which is reflected in up to ∼4 times lower leakage rates. Our work opens an easy way to improve the performance of graphene as a gas membrane on a technological relevant substrate such as SiO2We acknowledge financial support from the Spanish Ministry of Science and Innovation, through the “Marı́ ́ a de Maeztu” Programme for Units of Excellence in R&D (CEX2018- 000805-M), projects PID2019-106268GB, S2018/NMT-451, and FLAG-ERA JTC2017, and the Ramon Areces Foundation. G.L.-P. acknowledges financial support through the “Juan de la Cierva” Fellowship FJCI-2017-3237

First sexual intercourse and subsequent regret in three developing countries

Purpose: Adolescents who engage in sex can be affected by a range of negative physical and psychological consequences. We intend to analyze the reasons behind first sex, regret, and the association between reasons and regret. Methods: A questionnaire was implemented to 8495 high schools students, aged 14-18, in the Philippines, El Salvador and Peru. Sexually active participants responded whether several circumstances were reasons involved in their first sexual relationship. They also responded whether they regretted having already had sexual relationships. Results: More than a third of respondents reported at least one external pressure leading to first sex, and about half reported at least one reason implying getting carried away by sexual arousal. More females affirmed they regret having already had sex. Logistic regression shows that reasons for first sex associated with regret were partner insistence, "uncontrolled situations" and seeing sexual images. These reasons were associated with regret even when love was also reported as related to first sex. Conclusions: Adolescent sexual experience is often motivated by pressure and circumstances that lower the control over their decisions concerning sex, such as external pressure (because most friends already had sex or because of partner insistence) or getting carried away by sexual arousal (through an "uncontrolled situation" or viewing sexual images) rather than by mature decisions, and this may result in later regret. Adolescents should be helped by parents, educators and policy makers to be aware of these characteristics of adolescent sex and empowered to make assertive and informed decisions concerning their sexuality