Unexpected rearrangements in the synthesis of an unsymmetrical tridentate dianionic N-heterocyclic carbene

Starting from the same ethylenediamine species, three valuable carbene precursors were synthesized under differing conditions: a tridentate dianionic N-heterocyclic carbene bearing an aniline, a phenol and a central dihydroimidazolium salt, its benzimidazolium isomer by intramolecular rearrangement and a dicationic benzimidazolium-benzoxazolium salt by changing the Brønsted acid from HCl to HBF_4. A DFT study was performed to understand the rearrangement pathway. The structure of a bis[(NCO)carbene] zirconium complex was determined

Computational study on the iodobenzene-catalyzed oxidative cyclization of a δ-alkynyl β-ketoester

The iodobenzene-catalyzed oxidative cyclization of a δ-alkynyl β-ketoester has been investigated by density functional theory (DFT) calculations at the CPCM(acetonitrile)/B3LYP/6-311++G(d,p)//B3LYP/SDD(I) levels. Three different mechanisms were considered for this process, and of the three, activation of the alkyne by a hypervalent iodine species followed by cyclization was found to be the most likely pathway based upon our computational results

Characterization Study of CO2, CH4, and CO2/CH4 Hydroquinone Clathrates Formed by Gas–Solid Reaction

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO2 and CH4. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO2, pure CH4, and an equimolar CO2/CH4 mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and 13C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications

CO2–Hydroquinone Clathrate: Synthesis, Purification, Characterization and Crystal Structure

Organic clathrate compounds, particularly those formed between hydroquinone (HQ) and gases, are supramolecular entities recently highlighted as promising alternatives for applications such as gas storage and separation processes. This study provides new insights into CO2–HQ clathrate, which is a key structure in some of the proposed future applications of these compounds. We present a novel synthesis and purification of CO2–HQ clathrate monocrystals. Clathrate crystals obtained from a single synthesis and native HQ are characterized and compared using Raman/Fourier transform infrared/NMR spectroscopies, optical microscopy, and thermogravimetric analysis coupled to mass spectrometry. The molecular structure of the clathrate has been resolved by X-ray diffraction analysis, and detailed crystallographic information is presented for the first time

Silicon Differential Receiver With Zero-Biased Balanced Detection for Access Networks

[EN] We present an optimized differential receiver in silicon with a minimized footprint and balanced zero-biased Ge photodiodes. The receiver integrates a delay-line with a 2 ¿ 4 multimode interferometer 90° hybrid and two balanced photodiodes for differential quadrature phase-shift keying demodulation. Two receivers are tested, for 10 and 20 Gb/s operation, and well opened eye-diagrams and symbol constellations are obtained with error vector magnitude values as low as 12.5% and 19.57%, respectively. The results confirm the potential of integrated silicon receivers to become key building blocks for future passive optical access networks based on advanced modulation formats. © 1989-2012 IEEE.This work was supported in part by the European Community’s Seventh Framework Program under Grant 224312 HELIOS.Aamer, M.; Sotiropoulos, N.; Brimont, ACJ.; Fedeli, J.; Marris-Morini, D.; Cassan, E.; Vivien, L.... (2013). Silicon Differential Receiver With Zero-Biased Balanced Detection for Access Networks. IEEE Photonics Technology Letters. 25(13):1207-1210. https://doi.org/10.1109/LPT.2013.2262931S12071210251

The optoelectronic properties of new dyes based on thienopyrazine

International audienceIn this article, we present the quantum result of six dyes based on thienopyrazine (D1–D6) with donor–π–acceptor structure (D–π–A) using DFT/B3LYP/6-31G(d,p) and TD-DFT/CAM-B3LYP/6-31G(d,p) levels. The donor unit varied and the influence was investigated. The study of structural, electronic, and optical properties of these dyes could help design more efficient functional photovoltaic organic materials. Key parameters in close connection with the short-circuit current density (J sc ) including light harvesting efficiency, injection driving force (ΔG inject ), and total reorganization energy (λ total ) are discussed in this work

Performance of the CMS muon trigger system in proton-proton collisions at √s = 13 TeV

The muon trigger system of the CMS experiment uses a combination of hardware and software to identify events containing a muon. During Run 2 (covering 2015-2018) the LHC achieved instantaneous luminosities as high as 2 × 10 cm s while delivering proton-proton collisions at √s = 13 TeV. The challenge for the trigger system of the CMS experiment is to reduce the registered event rate from about 40 MHz to about 1 kHz. Significant improvements important for the success of the CMS physics program have been made to the muon trigger system via improved muon reconstruction and identification algorithms since the end of Run 1 and throughout the Run 2 data-taking period. The new algorithms maintain the acceptance of the muon triggers at the same or even lower rate throughout the data-taking period despite the increasing number of additional proton-proton interactions in each LHC bunch crossing. In this paper, the algorithms used in 2015 and 2016 and their improvements throughout 2017 and 2018 are described. Measurements of the CMS muon trigger performance for this data-taking period are presented, including efficiencies, transverse momentum resolution, trigger rates, and the purity of the selected muon sample. This paper focuses on the single- and double-muon triggers with the lowest sustainable transverse momentum thresholds used by CMS. The efficiency is measured in a transverse momentum range from 8 to several hundred GeV

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)