Helicene-based transition metal complexes: synthesis, properties and applications

International audienceThe coordination and/or organometallic chemistry of π-helicenic ligands appears as a powerfultool to generate multifunctional molecules displaying optimized chiroptical properties combinedwith new properties furnished by the metallic center. In this review, we relate the differentexamples that have been described in this field of research up to now

Feature-based Transferable Disruption Prediction for future tokamaks using domain adaptation

The high acquisition cost and the significant demand for disruptive discharges for data-driven disruption prediction models in future tokamaks pose an inherent contradiction in disruption prediction research. In this paper, we demonstrated a novel approach to predict disruption in a future tokamak only using a few discharges based on a domain adaptation algorithm called CORAL. It is the first attempt at applying domain adaptation in the disruption prediction task. In this paper, this disruption prediction approach aligns a few data from the future tokamak (target domain) and a large amount of data from the existing tokamak (source domain) to train a machine learning model in the existing tokamak. To simulate the existing and future tokamak case, we selected J-TEXT as the existing tokamak and EAST as the future tokamak. To simulate the lack of disruptive data in future tokamak, we only selected 100 non-disruptive discharges and 10 disruptive discharges from EAST as the target domain training data. We have improved CORAL to make it more suitable for the disruption prediction task, called supervised CORAL. Compared to the model trained by mixing data from the two tokamaks, the supervised CORAL model can enhance the disruption prediction performance for future tokamaks (AUC value from 0.764 to 0.890). Through interpretable analysis, we discovered that using the supervised CORAL enables the transformation of data distribution to be more similar to future tokamak. An assessment method for evaluating whether a model has learned a trend of similar features is designed based on SHAP analysis. It demonstrates that the supervised CORAL model exhibits more similarities to the model trained on large data sizes of EAST. FTDP provides a light, interpretable, and few-data-required way by aligning features to predict disruption using small data sizes from the future tokamak.Comment: 15 pages, 9 figure

Chiral Transmission to Cationic Polycobaltocenes over Multiple Length Scales Using Anionic Surfactants

International audienceChiral polymers are ubiquitous in nature, and the self-assembly of chiral materials is a field of widespread interest. In this paper, we describe the formation of chiral metallopolymers based on poly(cobaltoceniumethylene) ([PCE] ), which have been prepared through oxidation of poly(cobaltocenylethylene) (PCE) in the presence of enantiopure N-acyl-amino-acid-derived anionic surfactants, such as N-palmitoyl-l-alanine (C-l-Ala) and N-palmitoyl-d-alanine (C-d-Ala). It is postulated that the resulting metallopolymer complexes [PCE][C-l/d-Ala] contain close ionic contacts, and exhibit chirality through the axially chiral ethylenic CH-CH bridges, leading to interaction of the chromophoric [CoCp] units through chiral space. The steric influence of the long palmitoyl (C) surfactant tail is key for the transmission of chirality to the polymer, and results in a brushlike amphiphilic macromolecular structure that also affords solubility in polar organic solvents (e.g., EtOH, THF). Upon dialysis of these solutions into water, the hydrophobic palmitoyl surfactant substituents aggregate and the complex assembles into superhelical ribbons with identifiable "handedness", indicating the transmission of chirality from the molecular surfactant to the micrometer length scale, via the macromolecular complex

Disruption Precursor Onset Time Study Based on Semi-supervised Anomaly Detection

The full understanding of plasma disruption in tokamaks is currently lacking, and data-driven methods are extensively used for disruption prediction. However, most existing data-driven disruption predictors employ supervised learning techniques, which require labeled training data. The manual labeling of disruption precursors is a tedious and challenging task, as some precursors are difficult to accurately identify, limiting the potential of machine learning models. To address this issue, commonly used labeling methods assume that the precursor onset occurs at a fixed time before the disruption, which may not be consistent for different types of disruptions or even the same type of disruption, due to the different speeds at which plasma instabilities escalate. This leads to mislabeled samples and suboptimal performance of the supervised learning predictor. In this paper, we present a disruption prediction method based on anomaly detection that overcomes the drawbacks of unbalanced positive and negative data samples and inaccurately labeled disruption precursor samples. We demonstrate the effectiveness and reliability of anomaly detection predictors based on different algorithms on J-TEXT and EAST to evaluate the reliability of the precursor onset time inferred by the anomaly detection predictor. The precursor onset times inferred by these predictors reveal that the labeling methods have room for improvement as the onset times of different shots are not necessarily the same. Finally, we optimize precursor labeling using the onset times inferred by the anomaly detection predictor and test the optimized labels on supervised learning disruption predictors. The results on J-TEXT and EAST show that the models trained on the optimized labels outperform those trained on fixed onset time labels.Comment: 21 pages, 11 figure

Critical roles of edge turbulent transport in the formation of high-field-side high-density front and density limit disruption in J-TEXT tokamak

This article presents an in-depth study of the sequence of events leading to density limit disruption in J-TEXT tokamak plasmas, with an emphasis on boudary turbulent transport and the high-field-side high-density (HFSHD) front. These phenomena were extensively investigated by using Langmuir probe and Polarimeter-interferometer diagnostics

Hélicènes hétéroatomiques et organométalliques : synthèse et propriétés chiroptiques

Mes travaux de thèse se sont portés sur la synthèse d'hélicènes organométalliques et hétéroatomiques, et se divisent suivant trois axes majeurs. Le premier sujet est l'étude des hélicènes avec un centre métallique redox. Nous avons introduit un motif chimique contenant un atome de fer sur l'hélicène connecté par une liaison C≡C. Dans ce sujet, nous avons étudié les propriétés chiroptiques avec le changement d'état redox du centre métallique. Pour cela, nous avons utilisé des techniques spectroscopiques chiroptiques comme le dichroïsme circulaire vibrationnel, le spectre d'activité optique Raman qui opèrent dans la région infrarouge. Le deuxième sujet est l'étude d'hélicènes avec un centre rédox et un centre photochrome. Nous avons introduit l'hélicène sur un bloc chimique contenant du ruthénium connecté par liaison une C≡C, puis introduit le motif photochrome DTE (dithiényléthène) sur le ruthénium. La molécule contient donc trois parties : un centre chiral, un centre rédox et un centre photochrome. Dans ce sujet, nous avons étudié l'activité d'interrupteur chiroptique provoquée par un stimulus redox et/ou par la lumière. Le troisième sujet est l'étude de platinahélicènes et de borahélicènes qui sont issus de l'incorporation d'un ou deux platinacycles ou cycles azaboroles dans le squelette de l'hélicène. Dans ce sujet, nous avons examiné les propriétés optiques et chiroptiques, et étudié l'influence du nombre de cycles et du nombre d'hétérocycles. Ces produits ont également révélé des propriétés d'émission et de la luminescence polarisée circulairement.My PhD work has focused on the synthesis of organometallic and heteroatomic helicenes and is separated into three subjects. The first subject is the study of helicene with one redox metal center. We have introduced a building block containing an iron atom on the helicene connected by a C≡C bond. In this subject, we have studied the chiroptical properties with the change of the redox state of the metal center. Besides, we have used the techniques of chiroptical spectroscopies such as the vibrational circular dichroism, the Raman optical activity which occur in the infrared region. The second subject is the study of helicenes with one redox center and one photochromic center. We have introduced the helicene on the ruthenium building block, and then introduced a photochromic unit DTE (dithienylethene) on the ruthenium through C≡C bonds. This molecule contains three parts: one chiral center, one redox center and one photochromic center. In this subject, we have studied the redox- and/or light-triggered chiroptical switching activity. The third subject is the study on the platinahelicenes and borahelicenes which show one or two platinacycles or azaborole cycles incorporated in the helicene skeleton. In this subject, we have studied the optical and chiroptical properties, and also studied the influence of the number of cycles and number of the heterocycles. These compounds are also studied in the emission properties and circularly polarized luminescence

Fiber Sagnac interferometer for sensing magnetochiral birefringence: first tests on iron-alkynyl-helicenes

International audienceMagnetochiral (Mch) interaction leads to a small scalar contribution of the optical index of a chiral molecule on the direction of an external magnetic field. Mch-dichroism was first detected in Eu-complexes 1 and, since then, in various compounds such as, e.g., chiral ferromagnets or aggregates. Conversely, observation of Mch-birefringence (MchB) was only reported by two groups, using passive 2 or active interferometers. 3 However, for both setups, the response was polarization-dependent and required the availability of the two enantiomers of the compound under study, in order to compensate the circular anisotropies inherent to chiral samples. Recently, we have developed a home-made fiber Sagnac interferometer 4 dedicated to the measurement of directional phase shifts . It works at 6500 cm-1 and is optimized to be insensitive to circular anisotropies and to residual absorption. It can thus characterize MchB of samples i) for which the two enantiomers are not available and ii) of poor transmission. The detection floor is lim = 500 nrad.Hz-1/2 , only limited by the source intensity noise. We point out that, in order to reach this sensitivity, the so-called systematic effects have to be carefully circumvented. Here, we present this setup and focus on its use to probe the MchB of iron-alkynyl-helicenes. These molecules display giant chiroptical properties and have been shown to invert their optical rotation at 1.5 µm upon oxidation. 5 They are thus good candidates for investigating redox-triggered magnetochiral switching. Our samples consist in 0.5 ml of ethynyl-helicene mono or bis Fe II complexes (CH2Cl2, C≈15 mg/ml). Fig.1: Fe II complex Up-to-now, we have not detected any directional phase shift. This yields a 3-limit on the Mch-index of 6 10-13 T-1 at 1.55 μm for the helicenes tested. To increase the signal, we plan to probe MchB closer to the UV bands. A second-generation setup is now under test. It will work at 12000 cm-1 and should provide a better sensitivity due to lower intensity source and compactness. Finally, the potential detection of other chiroptical effects using our fiber interferometer will be discussed. (1) Rikken, G.L

DNA-induced circularly polarized luminescence of helicene racemates

International audienceEnantiopure helicenes have been extensively investigated due to their outstanding chiroptical properties, while helicene racemates are considered as chiroptically silent. Here, we describe a facile method to produce circularly polarized luminescence (CPL) from helicene racemates via supramolecular association with DNA in aqueous solution. Racemic cationic helicene derivatives are immobilized in the grooves of commercially available double-stranded right-handed DNA, and the discrimination of left- and right-handed helicenes by chiral DNA is monitored by single molecule force spectroscopy. This subsequently leads to the generation of prominent CPL with dissymmetric factor |g(lum)| of close to 0.01, which is approximate to enantiopure helicenes. The strategy developed in this work avoids the tedious and expensive chiral resolution process and provides a distinctive insight into the fabrication of CPL-emitting systems

Dual Redox and Optical Control of Chiroptical Activity in Photochromic Dithienylethenes Decorated with Hexahelicene and Bis-Ethynyl-Ruthenium Units

International audienceWe describe the synthesis of mono- and bis([6]helicene-≡-Ru(dppe)2-≡)-DTE complexes 1o,c and 2o,c. The photo-chromic and electrochromic properties were studied and attractive isomerization processes were observed, ie. spontaneous reopening of [1c] ·+ to [1o] ·+ and ring closure of [2o] 2+ to [2c] 2+. Due to strong chiroptical responses, all these chiral complexes correspond to new types of chiroptical switches (triggered by light and/or redox stimuli) and could be described as either " NOR " or " OR " logic gates

The Influence of Body Mass Index on Glucocorticoid Insensitivity in Chronic Rhinosinusitis with Nasal Polyps

Background: Reasons for glucocorticoid (GC) insensitivity in chronic rhinosinusitis with nasal polyps (CRSwNP) are not completely clear. Here, we investigate the influence of body mass index (BMI) on GC insensitivity in eosinophilic CRSwNP (eosCRSwNP) and noneosinophilic CRSwNP (noneosCRSwNP) patients. Methods: We recruited 699 CRSwNP patients and gave them a course of oral methylprednisolone for 2 weeks (24 mg/day). Patient demographics and clinical features were analyzed in both GC-sensitive and GC-insensitive CRSwNP patients with different BMI levels and phenotypes. Results: 35.3% of recruited CRSwNP patients were GC-insensitive, and the majority of GC-insensitive patients were males or prone to overweight & obese. Logistic regression analysis further confirmed that being overweight & obese was an independent risk factor for GC-insensitive of CRSwNP patients (odds ratio = 1.584, p = 0.049). Compared to underweight & normal-weight patients, overweight & obese patients were more likely to be GC insensitivity, particularly in the eosCRSwNP group, but not in the noneosCRSwNP group. However, there was no significant difference between the underweight & normal weight and the overweight & obese GC-insensitive eosCRSwNP patients regarding the number of infiltrated eosinophils, neutrophils, and polyp recurrence rate. Conclusions: Collectively, our findings demonstrate for the first time that BMI contributes to GC insensitivity in eosCRSwNP patients