A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15-1.73 GHz

We conducted a search for narrowband radio signals over four observing sessions in 2020-2023 with the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of ~11,680 stars and planetary systems in the ~9 arcminute beam of the telescope. All detections were either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. In this work, we also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable frequency range of the receiver and 98.7% of the injections when regions of dense RFI are excluded. In another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ~15 times smaller at ~6%. The pipeline efficiency affects calculations of transmitter prevalence and SETI search volume. Accordingly, we developed an improved Drake Figure of Merit and a formalism to place upper limits on transmitter prevalence that take the pipeline efficiency and transmitter duty cycle into account. Based on our observations, we can state at the 95% confidence level that fewer than 6.6% of stars within 100 pc host a transmitter that is detectable in our search (EIRP > 1e13 W). For stars within 20,000 ly, the fraction of stars with detectable transmitters (EIRP > 5e16 W) is at most 3e-4. Finally, we showed that the UCLA SETI pipeline natively detects the signals detected with AI techniques by Ma et al. (2023).Comment: 22 pages, 9 figures, submitted to AJ, revise

Suivi multi-descripteurs des réponses de microorganismes et de leurs consommateurs à une contamination en azurants optiques

International audienceLes azurants optiques, également connus sous le nom d’agents de blanchiment fluorescents (FWA), ont été détectés et identifiés dans plusieurs écosystèmes aquatiques. Cependant, leur toxicité sur le biote aquatique n’est à ce jour que très peu étudiée. Ils sont généralement utilisés pour augmenter la radiance spectrale totale pour blanchir les substrats. Ce sont donc des produits très répandus dans les industries du textile, du papier ou du plastique. Ils sont également ajoutés dans les détergents de lessive. L’objectif de ce projet est d’évaluer les effets des FWA sur les algues et les cyanobactéries ainsi que sur les biofilms périphytiques. Tout d’abord, des monocultures d’algues et de cyanobactéries seront exposées à une gamme de concentrations de FWA. Les profils des acides gras seront caractérisés, la bioaccumulation sera quantifiée, et l’inhibition de la photosynthèse des algues/cyanobactéries sera mesurée. La présence de tératologies (malformations) en réponse aux expositions sera aussi mesurée en utilisant des monocultures de diatomées. Sur la base de ces premiers résultats, une concentration en FWA sera sélectionnée pour une expérience sur des biofilms où les mêmes paramètres biologiques seront mesurés. Une expérience d’exposition sera finalement réalisée où des biofilms contaminés seront utilisés pour nourrir des escargots aquatiques (Limnaea stagnalis) sur une durée de 28 jours. Plusieurs descripteurs biologiques seront évalués tels que la mortalité, la croissance, le stress oxydatif et les profils en acides gras. Le potentiel de bioaccumulation du FWA dans les escargots en fonction des différentes voies d’exposition (trophique/aqueuse) sera également analysé

Method to Predict Reagents in Iridium-Based Photoredox Catalysis

Visible-light photoredox catalysts with oxidizing excited states have been broadly applied in organic synthesis. Following photon absorption by the photocatalyst, electron transfer from an organic reagent is the most common mechanistic outcome for this class of reaction. Reduction potentials for organic reagents are therefore useful to predict reactivity and DFT proved to be useful as a predictive tool in this regard. Due to the complex mechanisms that follow electron transfer, kinetics play a crucial role in the success of photoredox reactions. We extend the predictive tools of DFT to estimate the electron transfer rates between an excited photocatalyst and various organic substrates. To calibrate our model, 49 electron transfer rate constants were experimentally measured in acetonitrile for the catalyst Ir[dF(CF3)ppy]2(dtbpy)+. The rate constants, kq, gave a clear predictive trend when compared to calculated ionization energies in “frozen solvent”, which was a better predictor than standard reduction potentials in our case. The calculated kq gave an average error of 17% for log(kq) values between 4 and 11. This simple method can predict the reactivity of hundreds of reagents in silico. Notably, the calculations offered unexpected insight that we could translate into success for the C-H activation of acetylacetone as a proof-of-concept

Role of 18F-choline and 18F-fluorodeoxyglucose positron emission tomography in combination with magnetic resonance imaging in brachytherapy planning for locally advanced cervical cancer: A pilot study

Background and purpose: This pilot study aims to describe the advantages of combining metabolic and anatomic imaging modalities in brachytherapy (BT) planning for locally advanced cervical cancer (LACC) and to evaluate the supplementary value of Fluoro(F)-Choline positron emission tomography/computed tomography (PET/CT) in comparison to 18F-fluorodeoxyglucose (FDG) in this setting. Materials and methods: A prospective cohort of six patients with LACC was included in this study. Each patient underwent BT planning CT scan, magnetic resonance imaging (MRI), and both FDG and F-Choline PET/CT scans on the same day, with BT applicators in place. Patients were treated according to the standard of care. Metabolic target volumes (TV) were generated retrospectively and compared with the anatomic volumes using Dice coefficients and absolute volume comparison. Results: The threshold at which the metabolic and anatomic volumes were the most concordant was found to be 35% maximum standardized uptake value (SUV max) for both PET/CT scans. Amongst the six patients in this cohort, three in the FDG cohort and four in the F-Choline cohort were found to have more than ten percent ratio of excess (increase) in their MRI gross tumor volumes (GTV) when incorporating the metabolic information from the PET/CT scans. However, no significant changes were needed in the high risk-clinical target volumes (CTVHR) for both PET tracers. Conclusions: FDG and F-Choline PET/CT scans can substantially modify the BT GTV on MRI, without affecting the CTVHR. F-Choline is potentially more informative than FDG in assessing residual TV, particularly in cases with significant post-radiation inflammatory changes

Magnetically oriented bicelles with monoalkylphosphocholines: versatile membrane mimetics for nuclear magnetic resonance applications

Bicelles (bilayered micelles) are model membranes used in the study of peptide structure and membrane interactions. They are traditionally made of long- and short-chain phospholipids, usually dimyristoylphosphatidylcholine (D14PC) and dihexanoyl-PC (D6PC). They are attractive membrane mimetics because their composition and planar surface are similar to the native membrane environment. In this work, to improve the solubilization of membrane proteins and allow their study in bicellar systems, D6PC was replaced by detergents from the monoalkylphosphocholine (MAPCHO) family, of which dodecylphosphocholine (12PC) is known for its ability to solubilize membrane proteins. More specifically 12PC, tetradecyl- (14PC), and hexadecyl-PC (16PC) have been employed. To verify the possibility of making bicelles with different hydrophobic thicknesses to better accommodate membrane proteins, D14PC was also replaced by phospholipids with different alkyl chain lengths: dilauroyl-PC (D12PC), dipalmitoyl-PC (D16PC), distearoyl-PC (D18PC), and diarachidoyl-PC (D20PC). Results obtained by 31P solid-state nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC) at several lipid-to-detergent molar ratios (q) and temperatures indicate that these new MAPCHO bicelles can be formed under a variety of conditions. The quality of their alignment is similar to that of classical bicelles, and the low critical micelle concentration (CMC) of the surfactants and their miscibility with phospholipids are likely to be advantageous for the reconstitution of membrane proteins

Statin use moderates the beneficial effects of aerobic exercise on older adults' performances on the Stroop test: A subanalysis

International audienceAerobic training can lead to improved cognition in older adults and this effect can be explained by enhanced cardiorespiratory fitness. However, statins could limit the physical benefits of aerobic training by altering the mechanisms through which exercise improves cognition. Whether statins could have an effect on the cognitive benefits associated with aerobic training remains to be elucidated. The objective of this study was to determine whether the cognitive benefits of aerobic training were comparable in statin users and non-users. A total of 144 sedentary participants (>60 y.o.; 106 non-users, 38 statin users) were included. Participants were either part of an aerobic training group (n = 75) or a control group (n = 69). Cognition was assessed using the Stroop test. Analyses were performed on z-score changes from pre to post-intervention of Stroop reaction time (RT) and number of errors, using Two-factor ANCOVAs, while controlling for potential confounding factors (age, education, BMI, Charlson Comorbidity Index, sex, protocol and handgrip strength). The moderating effect of statins on the cognitive changes associated with aerobic training was determined through moderation analyses. An interaction effect on the Stroop switching condition was detected between intervention and statin intake (F [1, 140] = 5.659, P < 0.01). The intervention effect on switching RT was moderated by statin intake, where intervention improved switching RT only in non-users (Effect = 0.1678; P < 0.01). Statins could limit the cognitive benefits of aerobic training on switching capacities in some patients. Future randomized studies including a larger number of participants and looking at different types of statins should be conducted to confirm these results

Overcoming Challenges in Electrosynthesis Using High‐Throughput Electrochemistry: Hypervalent Iodine‐Mediated Phenol Dearomatization, a Case Study

Abstract Despite many recent efforts, the field of organic electrosyn‐thesis faces important challenges due to the intricate nature of heterogeneous redox processes, the wide parameter space to be explored and the lack of standardized methods. To overcome these limitations, we developed a cost‐effective high‐throughput electrochemical (HTE) reactor capable of running 24 individually controlled parallel reactions. This system allows the rapid testing of electrochemical parameters on a given reaction, assessing not only yield but also reproducibility. Using the hypervalent iodine‐mediated dearomatization of phloretic acid as a demonstration of HTE capabilities, we ran more than 200 electrosyntheses in different experimental conditions and demonstrate the effect of parameters such as total charge transferred, current, electrode materials, electrolyte formulation and concentration, mediator formulation and concentration and electrochemical technique of oxidation. Notably, this report demonstrates that while catalytic amounts of iodine mediator can be used successfully, the reproducibility may be affected, which calls for a cautious approach when developing similar transformations. Using cyclic voltammetry, density functional theory, chronopotentiometry, and Raman spectroscopy, we shed light on the causes of this issue

Metal-Free-Visible Light C–H Alkylation of Heteroaromatics via Hypervalent Iodine-Promoted Decarboxylation

A metal-free photoredox C–H alkylation of heteroaromatics from readily available carboxylic acids using an organic photocatalyst and hypervalent iodine reagents under blue LED light is reported. The developed methodology tolerates a broad range of functional groups and can be applied to the late-stage functionalization of drugs and drug-like molecules. The reaction mechanism was investigated with control experiments and photophysical experiments as well as DFT calculations