Role of Metal Contacts on Halide Perovskite Memristors

Halide perovskites are promising candidates for resistive memories (memristors) due to their mixed electronic/ionic conductivity and the real activation mechanism is currently under debate. In order to unveil the role of the metal contact and its connection with the activation process, four model systems are screened on halide perovskite memristors: Nearly inert metals (Au and Pt), low reactivity contacts (Cu), highly reactive contact (Ag and Al), and pre-oxidized metal in the form of AgI. It is revealed that the threshold voltage for activation of the memory effect is highly connected with the electrochemical activity of the metals. Redox/capacitive peaks are observed for reactive metals at positive potentials and charged ions are formed that can follow the electrical field. Activation proceeds by formation of conductive filaments, either by the direct migration of the charged metals or by an increase in the concentration of halide vacancies generated by this electrochemical reaction. Importantly, the use of pre-oxidized Ag+ ions leads to very low threshold voltages of ≈0.2 V indicating that an additional electrochemical reaction is not needed in this system to activate the memristor. Overall, the effect of the metal contact is clarified, and it is revealed that AgI is a very promising interfacial layer for low-energy applications.This study forms part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (CIGRIS/2022/150). The authors also thank the financial support of CONICET (External Fellowship 2020), Comunidad de Madrid (S2018/NMT-4326-SINFOTON2-CM), and of Universidad Rey Juan Carlos “Grupo DELFO de alto rendimiento”, reference M2363, under research program “Programa de fomento y desarrollo de la investigación”. C.G. would like to thank Generalitat Valenciana for a Grisolia grant (GRISOLIAP/2019/048). The authors thank the University Jaume I to allow for the use of Serveis Centrals d'Instrumentació Científica (SCIC)

Visible Light Communication System Using an Organic Bulk Heterojunction Photodetector

A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at -6 V.This work has been supported by Comunidad Autónoma de Madrid under project S2009/ESP-1781.Publicad

Epormenis cestri secretions in Sebastiania schottiana trees cause mass death of honey bee Apis mellifera larvae in Uruguay

For more than 60 years, sporadic cases of massive summer honey bee larvae mortality in colonies located near freshwater systems with abundant riparian vegetation have been reported in Uruguay. This odd phenomenon, known as “River disease” by beekeepers, can lead to colony death by depopulation. The aim of this study was to detect the causes of larvae death. Different experiments and analyses were performed using affected apiaries located between two important water courses. 1 day old larvae were the most susceptible and substances that killed the larvae were present in the nectar but not in the pollen. A palynological analysis of nectar samples showed that bees collect this resource from commonly pollinated floral species in the country. However, abundant fungi spores and conidia were found, which indicates that the bees also collected honeydews. In the riparian vegetation, bees were observed collecting the secretions of the planthopper Epormenis cestri on Sebastiania schottiana trees. It was found that the mortality period of larvae overlaps with the presence of E. cestri. Larvae maintained in the laboratory were fed (i) nectar from healthy colonies, (ii) nectar from affected colonies, and (iii) secretions of E. cestri. The mortality of the larvae that received nectar from colonies affected with River disease and secretions of E. cestri was higher than the mortality of those receiving nectar from healthy colonies. This represents the first report of planthopper honeydew causing mass larval mortality in honey bees

Leptin-resistant Zucker rats with trinitrobenzene sulfonic acid colitis present a reduced inflammatory response but enhanced epithelial damage

The study was funded the following grants of the Ministerio de Economía y Competitividad and the Fondo Europeo de Desarrollo Regional FEDER (SAF2011-22922, SAF2011-22812, BFU2014- 57736-P, and AGL2014-58883-R) and Junta de Andalucía (CTS164, CTS235, and CTS6736). B. Rivero-Guti errez, R. Gámez-Belmonte, and M. Arredondo-Amador were supported by fellowships from the Ministerio de Educación.The role of leptin in the development of intestinal inflammation remains controversial, since proinflammatory and anti-inflammatory effects have been described. This study describes the effect of the absence of leptin signaling in intestinal inflammation. Experimental colitis was induced by intrarectal administration of trinitrobenzene sulfonic acid (TNBS) to lean and obese Zucker rats (n = 10). Effects on inflammation and mucosal barrier were studied. Bacterial translocation and LPS concentration were evaluated together with colonic permeability to 4-kDa FITC-dextran. Obese Zucker rats showed a lower intestinal myeloperoxidase and alkaline phosphatase activity, reduced alkaline phosphatase sensitivity to levamisole, and diminished colonic expression of Nos2, Tnf, and Il6, indicating attenuated intestinal inflammation, associated with attenuated STAT3, AKT, and ERK signaling in the colonic tissue. S100a8 and Cxcl1 mRNA levels were maintained, suggesting that in the absence of leptin signaling neutrophil activation rather than infiltration is hampered. Despite the lower inflammatory response, leptin resistance enhanced intestinal permeability, reflecting an increased epithelial damage. This was shown by augmented LPS presence in the portal vein of colitic obese Zucker rats, associated with induction of tissue nonspecific alkaline phosphatase, LPS-binding protein, and CD14 hepatic expression (involved in LPS handling). This was linked to decreased ZO-1 immunoreactivity in tight junctions and lower occludin expression. Our results indicate that obese Zucker rats present an attenuated inflammatory response to TNBS, but increased intestinal epithelial damage allowing the passage of bacterial antigens.Ministerio de Economía y Competitividad and the Fondo Europeo de Desarrollo Regional FEDER (SAF2011-22922, SAF2011-22812, BFU2014- 57736-P, and AGL2014-58883-R)Junta de Andalucía (CTS164, CTS235, and CTS6736)Ministerio de Educació

Identification of Degradation Mechanisms in Slot-Die-Coated Nonfullerene ITO-Free Organic Solar Cells Using Different Illumination Spectra

In this work, we have studied degradation mechanisms of nonfullerene-based organic solar cells with PET/Ag/ZnO/PBDTB-T:ITIC/PEDOT:PSS/CPP PEDOT:PSS device structure. We compare pristine and degraded samples that were subjected to outdoor degradation following the standard ISOS-O2 protocol. The ideality factors for different incident wavelengths obtained from open-circuit voltage vs irradiation level and current density–voltage (J–V) measurements at different temperatures indicate that for aged samples recombination is governed by the Shockley–Read–Hall mechanism occurring in a region near the anode. Samples were also characterized using impedance spectroscopy (IS) and fitted to an electrical model. Impedance parameters were used to obtain mobility, indicating a clear degradation of the active layer blend for aged samples. The change in the chemical capacitance also reveals a worsening in carrier extraction. Finally, two-dimensional (2D) numerical simulations and fits to experimental J–V curves confirm the existence of a layer near the anode contact with poorer mobility and a decrease in the anode work function (WF) for the degraded samples.This work was supported by Comunidad de Madrid under the SINFOTON2-CM Research Program (S2018/NMT-4326-SINFOTON2-CM) and the Spanish Ministry of Economy, the Agencia Estatal de Investigación, and European Union's FEDER under the TEC2016−77242-C1/C2/C3 AEI/FEDER, UE Projects. The work of E.L.-F. was supported by the Ministerio de Educación y Formación Profesional for his Doctoral Grant through the FPU Research Fellowship under Grant FPU17/00612. M.M., J.L., E.D., and V.T. acknowledge that part of this work was developed within the RollFlex project, part-financed by Interreg Deutschland-Danmark with means from the European Regional Development Fund and the Southern Denmark Growth Forum. M.M. and V.T. acknowledge the support from the Villum Foundation for Project CompliantPV (Grant No. 13365). Finally, all authors acknowledge the support from the EU Framework Program Horizon 2020 for MNPS COST ACTION MP1307 StableNextSol.Publicad

MODELLING SOLAR CELL S-SHAPED I-V CHARACTERISTICS WITH DC LUMPED-PARAMETER EQUIVALENT CIRCUITS ­ A REVIEW

This article reviews and appraises the dc lumped-parameter equivalent circuit models that have been proposed so far for representing some types of solar cells that can exhibit under certain circumstances a detrimental S-shaped concave deformation within the energy-producing fourth quadrant of their illuminated I–V characteristics. We first present a very succinct recollection of lumped-parameter equivalent circuits that are commonly used to model conventional solar cells in general. We then chronologically present and discuss lumped-parameter equivalent sub-circuits that, combined with conventional solar cell equivalent circuits, are used to specifically represent the undesired S-shaped behaviour. The mathematically descriptive equations of each complete equivalent circuit are also examined, and closed form solutions for the terminal current and voltage as explicit functions of each other are presented and discussed whenever available. While comparing the most salient features and explaining the practical advantages and disadvantages of such equivalent circuit models, we offer some comments on possible directions for further improvement

An All-Organic Flexible Visible Light Communication System

Visible light communication systems can be used in a wide variety of applications, from driving to home automation. The use of wearables can increase the potential applications in indoor systems to send and receive specific and customized information. We have designed and developed a fully organic and flexible Visible Light Communication system using a flexible OLED, a flexible P3HT:PCBM-based organic photodiode (OPD) and flexible PCBs for the emitter and receiver conditioning circuits. We have fabricated and characterized the I-V curve, modulation response and impedance of the flexible OPD. As emitter we have used a commercial flexible organic luminaire with dimensions 99 × 99 × 0.88 mm, and we have characterized its modulation response. All the devices show frequency responses that allow operation over 40 kHz, thus enabling the transmission of high quality audio. Finally, we integrated the emitter and receiver components and its electronic drivers, to build an all-organic flexible VLC system capable of transmitting an audio file in real-time, as a proof of concept of the indoor capabilities of such a system.This Project was funded by Comunidad de Madrid through the SINFOTON-CM Research Program (S2013/MIT-2790), and the Spanish Ministry of Economy, the Agencia Estatal de Investigación and European Union's FEDER through the TEC2016-77242-C3-(1-R, 2-R and 3-R) AEI/FEDER, UE Projects

Actividad inhibitoria del extracto etanólico del Cyperus Rotundus procedente de la región de Cajamarca (provincia de Contumazá) en una cepa estandarizada de Streptococcus mutans (ATCC®25175)

Objective: The purpose of this study was to determine in vitro the inhibitory activity of the ethanolic extract of Cyperus rotundus (Cajamarca - Contumazá) against a standardize strain of Streptococcus mutans (ATCC®25175™). Materials and methods: This study was an experimental in vitro study, which consisted of determining the inhibitory effect of three concentrations of the ethanolic extract of Cyperus rotundus: 250 mg/ml, 500 mg/ml, and 1000 mg/ml against a strains of Streptococcus mutans (ATCC®25175™). Ten tests were performed for each concentration, having 0.12% chlorhexidine as a positive control for Streptococcus mutans plates and 10% DMSO as a negative control. To evaluate the inhibitory effect, the disk diffusion method or Kirby-Bauer test was used, reading the results at 48 hours after initial sowing. Results: None of the three concentrations of the ethanolic extract of Cyperus rotundus demosntrated inhibitory effects on the Streptococcus mutans strain; however, the positive control, chlorhexidine, clearly showed inhibition halos of 14.43 mm ± 1.23 mm after 48 hours of incubation. Conclusions: The ethanolic extract of Cyperus rotundus did not inhibit the growth of Streptococcus mutans. It is recommended to deepen the chemical analysis of the components of this plant and explore other extraction methods to verify its bacteriostatic action versus other oral and non-oral microorganisms.Objetivo: Determinar in vitro la actividad inhibitoria del extracto etanólico del Cyperus rotundus (Contumazá, Cajamarca) frente a una cepa estandarizada de Streptococcus mutans (ATCC®25175TM). Materiales y métodos: El presente estudio fue de tipo experimental in vitro, el cual consistió en determinar el efecto inhibitorio de tres concentraciones del extracto etanólico de Cyperus rotundus: 250 mg/ml, 500 mg/ml y 1000 mg/ml frente a Streptococcus mutans (ATCC®25175TM). Se realizaron 10 pruebas para cada concentración del extracto, y se tuvo como control positivo la clorhexidina al 0,12% y como control negativo, al DMSO al 10%. Para evaluar el efecto inhibitorio, se utilizó el método de difusión en discos o prueba de Kirby-Bauer, y se realizó la lectura de las placas de cultivo a las 48 horas posteriores a la siembra. Resultados: Ninguna de las tres concentraciones del extracto etanólico de Cyperus rotundus presentó efecto inhibitorio para la cepa de Streptococcus mutans; sin embargo, tras el control positivo, la clorhexidina presentó halos de inhibición de 14,43 mm ± 1,23 mm, a las 48 horas de incubación. Conclusiones: Se determinó que el extracto etanólico del Cyperus rotundus no es capaz de inhibir el crecimiento de Streptococcus mutans. Se recomienda profundizar en el análisis químico de los componentes de esta planta y explorar otros metodos de extracción para verificar su acción bacteriostática en otros microorganismos orales y no orales

Perfiles virales de colonias susceptibles y sobrevivientes a Varroa destructor

Varroa destructor es la principal amenaza biótica de Apis mellifera, es vector de diversos virus y es letal si las colonias no son tratadas a tiempo. En Uruguay existe una población de abejas que sobreviven naturalmente a la parasitación con este ácaro sin necesidad de tratamientos. Este fenómeno estaría asociado a un mayor comportamiento higiénico de esas abejas; pero, además, podría deberse a la presencia de comunidades virales diferenciales asociadas a las colonias. El objetivo de este trabajo fue cuantificar y caracterizar los virus presentes en colonias de A. mellifera sobrevivientes y susceptibles a V. destructor de nuestro país. Para ello se tomaron muestras de abejas nodrizas de estas colonias en primavera y en otoño, y se realizó la detección y cuantificación absoluta mediante qPCR de los virus: de la Parálisis Aguda (ABPV), de las Celdas Reales Negras (BQCV), de las Alas Deformes (DWV) y de la cría ensacada (SBV). Paralelamente, muestras de esas mismas colonias fueron sometidas a protocolos de enriquecimiento de las partículas virales y posterior secuenciación masiva (Illumina). Los resultados de este trabajo nos permitieron realizar la caracterización genómica de los principales virus de interés apícola (ABPV, BQCV, DWV y SBV). A su vez, se observó que en otoño las colonias sobrevivientes presentaron menor nivel de infección para algunos virus comparado con las colonias susceptibles. Por último, la secuenciación masiva permitió la detección de algunos fragmentos de virus que aún no se habían detectado en nuestro país, como el Virus del Lago Sinaí y el Virus Filamentoso de Apis mellifera. Continuamos estudiando los perfiles virales de las colonias sobrevivientes y susceptibles a V. destructor con el fin de avanzar hacia un control sustentable de las poblaciones de ácaros.Agencia Nacional de Investigación e Innovació