Phosphonium dicyanamide ionogel incorporating bromophenol blue dye as a versatile platform for monitoring pH in solution

Online monitoring of pH levels in different environments such as bio-engineering and chemistry is vital for effective control of many critical industrial processes. The most common chemical parameter monitored is pH, and there is an increasing interest in the fabrication of robust, cheap and versatile pH sensing materials that can be easily integrated within existing industrial technologies. Ideally these materials present low fouling and do not require calibration, thus minimising manual attention over long operational intervals. In this work we present an innovative material (ionogel) that integrates pH-sensing capabilities for continuously measuring pH during chemical or biological processes. The ionogel is a solid, flexible and easily to pattern material generated using tetrabutylphosponium dicyanamide ionic liquid, hydrogel polymer (N-isopropylacrylamide and N,N-methylene-bis(acrylamide)) and a pH sensitive dye (Bromophenol Blue). Figure 1 shows the UV spectra of the ionogel-dye in an acidic and a basic pH environment as well as the pictures of the ionogels. A substantial colour variation is observed as the pH changes that can be monitored visually or optically. We incorporated the photoresponsive dye during photo-polymerisation of the monomer to improve stability, for example, by preventing leaching of the dye from the ionogel into the sample phase. This strategy was not found to inhibit the sensitivity of the optical response

Daily variability of Ceres' Albedo detected by means of radial velocities changes of the reflected sunlight

Bright features have been recently discovered by Dawn on Ceres, which extend previous photometric and Space Telescope observations. These features should produce distortions of the line profiles of the reflected solar spectrum and therefore an apparent radial velocity variation modulated by the rotation of the dwarf planet. Here we report on two sequences of observations of Ceres performed in the nights of 31 July, 26-27 August 2015 by means of the high-precision HARPS spectrograph at the 3.6-m La Silla ESO telescope. The observations revealed a quite complex behaviour which likely combines a radial velocity modulation due to the rotation with an amplitude of approx +/- 6 m/s and an unexpected diurnal effect. The latter changes imply changes in the albedo of Occator's bright features due to the blaze produced by the exposure to solar radiation. The short-term variability of Ceres' albedo is on timescales ranging from hours to months and can both be confirmed and followed by means of dedicated radial velocity observations.Comment: 5 pag, 1fig, two tables, MNRAS Letters 201

Strong antenna-enhanced fluorescence of a single light-harvesting complex shows photon antibunching

The nature of the highly efficient energy transfer in photosynthetic light-harvesting complexes is a subject of intense research. Unfortunately, the low fluorescence efficiency and limited photostability hampers the study of individual light-harvesting complexes at ambient conditions. Here we demonstrate an over 500-fold fluorescence enhancement of light-harvesting complex 2 (LH2) at the single-molecule level by coupling to a gold nanoantenna. The resonant antenna produces an excitation enhancement of circa 100 times and a fluorescence lifetime shortening to ~\n20 ps. The radiative rate enhancement results in a 5.5-fold-improved fluorescence quantum efficiency. Exploiting the unique brightness, we have recorded the first photon antibunching of a single light-harvesting complex under ambient conditions, showing that the 27 bacteriochlorophylls coordinated by LH2 act as a non-classical single-photon emitter. The presented bright antenna-enhanced LH2 emission is a highly promising system to study energy transfer and the role of quantum coherence at the level of single complexes

Concept and development of an autonomous wearable micro-fluidic platform for real time pH sweat analysis

In this work the development of an autonomous, robust and wearable micro-fluidic platform capable of performing on-line analysis of pH in sweat is discussed. Through the means of an optical detection system based on a surface mount light emitting diode (SMD LED) and a light photo sensor as a detector, a wearable system was achieved in which real-time monitoring of sweat pH was performed during 55 minutes of cycling activity. We have shown how through systems engineering, integrating miniaturised electrical components, and by improving the micro-fluidic chip characteristics, the wearability, reliability and performance of the micro-fluidic platform was significantly improved

Modelação e Previsão do fluxo de Turismo em Portugal: Perspetivas para uma gestão estratégica

Purpose: The increase of Tourism in Portugal, as well as the companies related to it, it is necessary to analyze and forecast the flow of tourists so that the management of the business is endowed with a competitive strategy. Given the changes in the 'recent' dynamics of tourism data, this article discusses the contributions and limitations of using classical forecasting methodologies, when applied to this sector, namely to the number of overnight stays in tourist accommodation establishments in Portugal. Methodology: The study focuses on the modeling and forecasting of time series related to the number of monthly overnight stays, in tourist accommodation establishments in Portugal, between January 2002 and March 2022. As a result of some suggestions contained in the scientific literature, it was resorted the Exponential Smoothing (ETS) methodologies. In computational terms, we used the Jupyter computational environment, with the Python programming language (version 3.7.3). Findings: The results were presented and discussed through the analysis of two time series: (1) Total number of overnight stays in tourist accommodation establishments in Portugal – Total series; (2) Number of overnight stays spent by residents in Portugal in tourist accommodation establishments in Portugal – Residents series. Overall, from the analysis of the time series, there was a growth of Tourism in Portugal since 2002, with a visible drop in 2020, due to the pandemic situation. Regarding the ETS methodologies used in the modeling and forecasting, although they corresponded positively in the forecast of the Total series (with some error), the same did not happen in the Residents series. In this series, due to the recent dynamics that are completely atypical, it appears that the ETS methodologies, potentially more adequate, do not converge, in general. However, it is important to mention that it was the overnight stays of residents that, in the pandemic period, dictated the dynamics present in the Total series. Research limitations: The literature points to a good performance of ETS methodologies in time series with characteristics present in the series under study (with the presence of a trend cycle and clear seasonality), a fact that motivated its choice. However, the difficulty of these methodologies in dealing with abrupt breaks in the data history was evident in this study. Despite how adjusted the forecasts are, the highlight is the non-convergence of some models that could be better adjusted to the historical data. In this sense, it is necessary to search for alternative forecasting methodologies, where Machine Learning methodologies, namely Deep Learning (Deep Neural Networks) have been pointed out in the scientific literature as quite promising. This will be the next step of the investigation. Originality: Given the importance that Tourism has both in the economic and social dimension of Portugal, and being a very volatile and constantly changing sector, it is imperative to define a strategy for future action to understand how, internally, the sector can define policies to avoid situations of external dependence. In addition to a current analysis of the data history, resulting from an atypical period of pandemic, we need to critically evaluate the predictive capacity of (classical) econometric models, which can be used by the industry related to tourism. This not only contributes to a better understanding of the phenomenon under study, but also constitutes a tool to support decision-making.info:eu-repo/semantics/publishedVersio