Photochromic heteroarylethenes with fast thermal isomerization kinetics

Supplementary data to this article can be found online at https://doi.org/10.1016/j.dyepig.2022.111000Stilbenes (diphenylethenes) are fully examined organic chromophores for very diverse applications. However, these molecules might show poor stability under irradiation because several simultaneous reactions (oxidative photocyclization and dimerization) can take place during the photochemical isomerization of their C=C bond. In this context, heteroarylethenes emerge as powerful counterparts thanks to their improved stability. In addition, the chosen heterocycles and their functionalization allows to fine tune and increase the speed at which the thermal back reaction occurs, broadening the scope of application of the resulting chromophores. Here we report on the thermal Z-to-E isomerization kinetics of a series of rationally designed heteroarylethenes and how the chemical architecture of the chromophore modulates the speed of the process. Specifically, the metastable Z isomers display relaxation times covering a wide time window, from a few hours to hundreds of microseconds. In fact, one of the studied dyes is the fastest heteroarylethene known to date. It should be also noticed that the described heteroarylethenes exhibit great photochemical stability, it being possible to switch them back and forth many times without degradation.This research was funded by the Ministerio de Ciencia, Innovacion y Universidades (Spain)/Agencia Estatal de Investigacion (Spain)/Fondo Europeo de Dearrollo Regional (FEDER, European Union), grant number PGC2018-095477-B-I00. Thanks are also due to Fundação para a Ciência e Tecnologia (FCT) and to FEDER-COMPETE for financial support through the research center CQUM (UID/QUI/0686/2016) and (UID/ QUI/0686/2020). The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project Nº 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC). Authors also thank Prof. Santi Nonell for granting access to the nanosecond laser flash photolysis setup

Minimum Conductivity and Evidence for Phase Transitions in Ultra-clean Bilayer Graphene

Bilayer graphene (BLG) at the charge neutrality point (CNP) is strongly susceptible to electronic interactions, and expected to undergo a phase transition into a state with spontaneous broken symmetries. By systematically investigating a large number of singly- and doubly-gated bilayer graphene (BLG) devices, we show that an insulating state appears only in devices with high mobility and low extrinsic doping. This insulating state has an associated transition temperature Tc~5K and an energy gap of ~3 meV, thus strongly suggesting a gapped broken symmetry state that is destroyed by very weak disorder. The transition to the intrinsic broken symmetry state can be tuned by disorder, out-of-plane electric field, or carrier density

Fastest non-ionic azo dyes and transfer of their thermal isomerisation kinetics into liquid-crystalline materials

Push-pull bithienylpyrrole-based azo dyes exhibit thermal isomerisation rates as fast as 1.4 μs in acetonitrile at 298 K becoming, thus, the fastest neutral azo dyes reported so far. These remarkably low relaxation times can be transferred into liquid-crystalline matrixes enabling light-triggered oscillations in the optical density of the final material up to 11 kHz under ambient conditions.Financial support for this research was obtained from the Ministerio de Economía y Competitividad (Spain, CTQ2012-36074 and CTQ2015-65770-P). The authors thank Prof. Santi Nonell for his help with the flash photolysis measurements. Thanks are also due to: Fundação para a Ciência e Tecnologia (FCT) for a PhD grant to M. C. R. Castro (SFRH/BD/78037/2011); FEDERCOMPETE for financial support through the Centro de Quı ´mica – UM, PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT

The effect of oxygen pickup during selective laser melting on the microstructure and mechanical properties of Ti–6Al–4V lattices

Additive manufacturing techniques such as Selective Laser Melting (SLM) can produce complex shapes with relatively thin sections and fine detail. However, common materials for the process, such as Ti–6Al–4V, have microstructure and properties that are sensitive to the pickup of interstitial impurities, such as oxygen, which the material will be exposed to during the process. This problem would be especially severe for parts with thin sections, where surface effects can be more significant, and where poor properties may coincide with locally-elevated stress. Here we explore the effects of oxygen level in thin sections with the use of lattice materials (materials which can be considered to consist exclusively of near-surface material). Oxygen levels are artificially raised using repeated melting passes to result in more pickup, leading to significantly reduced ductility and hence reduced strength measured in compression. A ductile to brittle transition in strut failure mechanism is found with increasing number of melting passes, with significant modification in chemistry and crystallographic structure, despite the presence of a similar fine plate-like microstructure throughout

Molecular photo-oscillators based on highly accelerated heterocyclic azo dyes in nematic liquid crystals

Benzothiazole-pyrrole-based azo dyes enhance greatly their thermal isomerisation rate up to 160 times when they are under the influence of the nematic mean field yielding the LC-based photochromic oscillators with the highest oscillation frequencies reported so far (2.6 kHz at 298 K).Fundação para a Ciência e a Tecnologia (FCT

Adaptable photochromic switches with self-aggregating heterocyclic azo dyes

It is well-known that the thermal isomerization kinetics of photochromic azo dyes can be modulated by subtle changes in their chemical architecture. However, the availability of an orthogonal input to control the thermal relaxation of azo dyes is essential to enable access to multifunctional and adaptive photochromic switches based on these particular organic chromophores. In this work, we have designed and synthesized a new family of green-light-activated heterocyclic azo derivatives that modify their switching capabilities as a function of concentration. In this line, we have investigated their self-assembly and the nature of the supramolecular aggregates formed by means of dynamic light scattering, polarized optical microscopy, and X-ray diffraction. Indeed, imparting control over the self-assembly of these organic dyes allows to fine-tune their thermal relaxation time and produce adaptable photochromic switches. Specifically, swapping the azo dye concentration between values located above and below the corresponding critical aggregation concentration modifies significantly the relaxation time up to 250 times, i.e., from the millisecond to the microsecond timescale. Moreover, the optical density of the system can be switched back and forth hundreds of times, for both diluted and concentrated solutions, without any sign of fatigue.Financial support for this research was obtained from the Ministerio de Economia y Competitividad (Spain, PGC2018-095477-B-I00, CTQ2016-78454-C2-1-R, and CTQ2017-84998-P MINECO/FEDER). Thanks are also due to Fundacao para a Ciencia e Tecnologia (Portugal) for financial support to the Portuguese NMR network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT, and FEDER (European Fund for Regional Development)-COMPETEQREN-EU for financial support to the research centre CQ/UM [ref UID/QUI/00686/2013 and UID/QUI/0686/2016], and a PhD grant to M.C.R.C. (SFRH/BD/78037/2011)

Experimental demonstration of machine-learning-aided QoT estimation in multi-domain elastic optical networks with alien wavelengths

In multi-domain elastic optical networks with alien wavelengths, each domain needs to consider intradomain and interdomain alien traffic to estimate and guarantee the required quality of transmission (QoT) for each lightpath and perform provisioning operations. This paper experimentally demonstrates an alien wavelength performance monitoring technique and machine-learning-aided QoT estimation for lightpath provisioning of intradomain/interdomain traffic. Testbed experiments demonstrate modulation format recognition, QoT monitoring, and cognitive routing for a 160 Gbaud alien multi-wavelength lightpath. By using experimental training datasets from the testbed and an artificial neural network, we demonstrated an accurate optical-signal-to-noise ratio prediction with an accuracy of ∼95% when using 1200 data points

Water Masses and Circulation in the Tropical Pacific off Central Mexico and Surrounding Areas

13 páginas, 8 figuras, 2 tablasThe seasonal variations and the interactions of the water masses in the tropical Pacific off central Mexico (TPCM) and four surrounding areas were examined based on an extensive new hydrographic database. The regional water masses were redefined in terms of absolute salinity (SA) and conservative temperature (Θ) according to the Thermodynamic Equation of Seawater 2010 (TEOS-10). Hydrographic data and the evaporation minus (precipitation + runoff) balance were used to investigate the origin and seasonality of two salinity minima in the area. The shallow (50–100 m) salinity minimum originates with the California Current System and becomes saltier as it extends southeastward and mixes with tropical subsurface waters while the surface salinity minimum extends farther north in the TPCM in summer and fall because of the northward advection of tropical surface waters. The interactions between water masses allow a characterization of the seasonal pattern of circulation of the Mexican Coastal Current (MCC), the tropical branch of the California Current, and the flows through the entrance of the Gulf of California. The seasonality of the MCC inferred from the distribution of the water masses largely coincides with the geostrophic circulation forced by an annual Rossby waveThis is a product of the project CONACyT (SEP2011–168034-T), with collaboration from the following sources: CONACyT Projects 168034-T, T-9201, 4271P-T, 38797-T, 26653-T, 1076-T9201, 4271PT9601, C01–25343; 38834-T, C02-44870F,G34601-S, and 103898; Naval Postgraduate School; NOC-US; NOAA (GC04– 219); and the regular UABC budget through Projects 4009, 4015, 0324, 0333, and 0352. Funding came from CONACyT, México through the Grant 1329234 for the Ph.D. studies of Esther PortelaPeer reviewe

Tratamento com implantes dentários pós-extração.

Introduction: The aim of the present study was to show the results of treatment with dental implants inserted immediately after extraction. Methods: 22 patients with unitary, partial or total tooth loss were treated with 82 Microdent ® implants with etched and acid-etched surfaces. All implants were inserted immediately after the corresponding extraction. The implants were loaded after a healing period of 3 months in the mandible or 6 months in the upper mandible. Results: Clinical findings indicate survival and implant success of 97.6%. 2 implants were lost during the healing period. 73.2% of the implants were inserted in the  maxilla, while 26.8% in the mandible. After an average functional load period of 12 months, there were no late complications. Conclusions: This study indicates that dental implants inserted immediately after extraction can be a predictable and successful alternative to the implant.  Introdução: O objetivo do presente estudo foi mostrar os resultados do tratamento com implantes dentários inseridos imediatamente após a extração. Métodos: 22 pacientes com perda dentária unitária, parcial ou total foram tratados com 82 implantes Microdent ® com superfície tratada com ácidos. Todos os implantes foram inseridos imediatamente após a extração correspondente. Os implantes foram carregados após um período de cicatrização de 3 meses na mandíbula ou 6 meses na maxila. Resultados: Os achados clínicos indicam sobrevivência e sucesso dos implantes de 97,6%. 2 implantes foram perdidos durante o período de cicatrização. 73,2% dos implantes foram inseridos na maxila, enquanto 26,8% na mandíbula. Após um período médio de carga funcional de 12 meses, não houve complicações tardias. Conclusões: Este estudo indica que implantes dentários inseridos imediatamente após a extração podem ser uma alternativa previsível e bem-sucedida ao implante

The Role of Endocrine Disrupting Chemicals in Gestation and Pregnancy Outcomes

This research was funded by the Plan Propio de Investigación de la Universidad de Granada of Spain (grant number PP2022.PP-07). J.M.T. and M.P.-J. are grateful to the Ph.D. Excellence Program “Nutrición y Ciencias de los Alimentos” from the University of Granada. J.M.T. was supported by an FPU contract with grant reference FPU21/04865 funded by the Ministry of Education of Spain.Endocrine disrupting chemicals (EDCs) are exogenous substances widely disseminated both in the environment and in daily-life products which can interfere with the regulation and function of the endocrine system. These substances have gradually entered the food chain, being frequently found in human blood and urine samples. This becomes a particularly serious issue when they reach vulnerable populations such as pregnant women, whose hormones are more unstable and vulnerable to EDCs. The proper formation and activity of the placenta, and therefore embryonic development, may get seriously affected by the presence of these chemicals, augmenting the risk of several pregnancy complications, including intrauterine growth restriction, preterm birth, preeclampsia, and gestational diabetes mellitus, among others. Additionally, some of them also exert a detrimental impact on fertility, thus hindering the reproductive process from the beginning. In several cases, EDCs even induce cross-generational effects, inherited by future generations through epigenetic mechanisms. These are the reasons why a proper understanding of the reproductive and gestational alterations derived from these substances is needed, along with efforts to establish regulations and preventive measures in order to avoid exposition (especially during this particular stage of life).Universidad de Granada PP2022.PP-07Ministry of Education of Spain FPU21/0486