Fluorescence studies of Langmuir—Blodgett films of chlorophyll a mixed with phytol

The fluorescence properties of chlorophyll a mixed with phytol (in a 1:100 molar ratio) were studied in Langmuir—Blodgett films. Fluorescence excitation and fluorescence emission spectra of the chlorophyll a-phytol system in Langmuir—Blodgett films, prepared from an argon-saturated subphase, have maxima at 444 nm and 684 nm respectively. Two lifetime components describe the state of chlorophyll a in Langmuir—Blodgett films: τ 1 = 5.18 ns (33%) and τ 2 = 1.83 ns (67%); these are assigned to single molecules of chlorophyll a and to hydrated dimers or oligomers of chlorophyll a respectively. For films prepared from an oxygen-saturated subphase, the maxima of the fluorescence excitation and fluorescence emission spectra of the chlorophyll a-phytol system are shifted to 423 nm and 678 nm respectively. The lifetime components in the time-resolved fluorescence decay curve of the film are τ 1 = 3.81 ns (54%) and τ 2 = 1.56 ns (46%). The observed changes in the fluorescence parameters of the chlorophyll a-phytol Langmuir—Blodgett films are discussed in view of the chemical effect of molecular oxygen on the mixed chlorophyll a-phytol monolayer at the air—water interface

Local Perceptions, Ruslefac Mapping, and Field Results: The Sediment Budget of Cocagne River, New Brunswick, Canada

International audienceErosion and sedimentation in water courses represent a major and costly problem everywhere on the planet. Perception of local actors of the state of the river can be a useful source of information to document the river’s changes. The main objective of this study consists of understanding how multiple data sources can be used for identifying the most sensitive areas subject to erosion and sedimentation in a watershed. To achieve our objective we combined three complementary methods: conducting interviews, estimating the most sensitive soil loss areas using the Revised Universal Soil Loss Equation for Application in Canada (RUSLEFAC) and taking measurements of environmental variables (turbidity, deposition rate, particle size, water quality, rainfall). The information gathered from the interviews allowed us to determine which areas were the most affected (e.g., either erosion or deposition). However, we observed that there were some differences between the areas identified by the participants and those obtained from the RUSLEFAC and in situ measurements. Among these differences, participants identified sites which were the results of misuse or bad practices (e.g., ATV). By contrast sensitive sites for erosion, as identified using RUSLEFAC, are instead areas of steep slopes, located near the river without forest cover. The in situ measurements were very helpful in establishing background values for turbidity but also for comparing quantitative information (e.g., particle size) with what was reported in the interviews

Aggregation of chlorophylls a and b in polymer films and monolayers

Polarized absorption and fluorescence spectra as well as lifetime of fluorescence (τ) of the mixtures of chlorophyll a (Chl a) and chlorophyll b (Chl b) in anisotropic polyvinyl alcohol (PVA) films were measured. Two mixtures with various concentrations ratios of Chl a to Chl b were investigated. For comparison, the fluorescence excitation and emission spectra of Chl b + phytol mixture in Langmuir—Blodgett films were also measured. At high Chl a and low Chl b concentrations (MI) the following three forms of Chl a aggregates occurred: ‘dry’ Chl a (aggregated with polymer) with a fluorescence maximum at 676 nm (F676), hydrated dimer (Chl a 2H 2O) 2 or (Chl a H 2O) 2 (F700–705 nm), and oligomers of hydrated dimers (F750–770 nm). Chl b in the same matrix also occurs in at least three forms: ‘dry’ (F653 nm), ‘wet’ - hydrated aggregates (F662 nm) and aggregated forms with the fluorescence at 710–720 nm and/or 730–740 nm regions. The orientation of various chlorophyll forms in the PVA matrix is different. The efficiency of excitation energy transfer from Chl b to various aggregates of Chl a is different. The yield of energy transfer from Chl b to Chl a oligomers is high. Fluorescence decay of various aggregates is different and the experimental decay can be analysed always on two or three exponential components. Results are discussed on the basis of previous data concerning the monolayers of Chl a with phytol and literature data concerning aggregation of chlorophylls in various model systems. In the spectra of chlorophyll in several model systems, as follows from the literature, it is possible to distinguish the contributions from the three or even more aggregated forms of pigment similar to those reported by us. Some similarities between aggregated forms or chlorophylls and pigment forms observed in organisms are noted. In polymer films, aggregated forms of pigments are stable and oriented; therefore, their properties and the condition of their formation can be established

La classe en islam : entre piété et distinction

Les recherches académiques sur l’islam intègrent rarement l’appartenance à une classe sociale comme critère d’analyse, différenciant plutôt les musulman.e.s par leurs divergences dogmatiques (soufies, salafistes, etc.). Or, dans les contextes régionaux contemporains d’Afrique centrale, de l’Ouest et du Nord, reconfigurés par les violences djihadistes, nombre de musulman.e.s redéfinissent les normes de leur « bonne religiosité » en jouant sur des marqueurs de classe. Majoritairement axées sur les musulmanes, figures centrales de ces nouvelles configurations de religiosités, les études de cas présentées dans ce numéro montrent qu’une appartenance de classe — entendue en termes socioéconomiques, mais aussi en fonction de pratiques (culturelles, matérielles) où s’expriment des sentiments d’adhésion à un groupe — influe sur les façons d’être et de se montrer musulman.e ; et qu’en retour, l’affirmation de pratiques religieuses renforce un sentiment de différenciation sociale. Les contextes urbains, où les « classes moyennes émergentes » sont les plus visibles, sont privilégiés pour poser la question d’une éventuelle corrélation entre volonté d’ascension sociale et prétention à une élévation morale et religieuse. Academic research on Islam rarely includes an analysis of social classes as a means to think about social differentiation between Muslims. Dogma (Sufis, Salafists, etc.) is the primary angle through which differences amongst Muslims are studied. Yet, in the contemporary regional contexts of Africa, especially North, West and Central Africa, where jihadist violence has reconfigured existing social belongings, many Muslims are redefining the norms of “good religiosity” through class markers. Focused mainly on Muslim women as central figures in these renewed forms of religiosity, the case studies presented in this issue show that class belonging, understood in socio-economic terms but also through embodied cultural and material practices, compels individual and group assertions of Muslimhood. In a reciprocal manner, the upholding of specific practices reinforces a sense of social differentiation. Urban contexts, where the “emerging middle classes” are most visible, are privileged sites to question a possible connection between the desire for social ascension and the claim to moral and religious elevation

Prehospital Lyophilized Plasma Transfusion for Trauma-Induced Coagulopathy in Patients at Risk for Hemorrhagic Shock

International audienceIMPORTANCE Blood transfusion is a mainstay of therapy for trauma-induced coagulopathy, but the optimal modalities for plasma transfusion in the prehospital setting remain to be defined. OBJECTIVE To determine whether lyophilized plasma transfusion can reduce the incidence of trauma-induced coagulopathy compared with standard care consisting of normal saline infusion. DESIGN, SETTING, AND PARTICIPANTS This randomized clinical trial was performed at multiple centers in France involving prehospital medical teams. Participants included 150 adults with trauma who were at risk for hemorrhagic shock and associated coagulopathy between April 1, 2016, an