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Enantioselective iridium-catalyzed allylic substitution with a Reformatsky reagent: direct construction of β-stereogenic homoallylic esters

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Science China Chemistry 2024年第11期67卷 3791-3797页

作者： debasis pal Kirana d.Veeranna Yuk Fai Wong p.Andrew Evans department of Chemistry Queen's University Xiangya School of pharmaceutical Sciences Central South University

The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio-and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate. Notably, this work represents the first example of using a Reformatsky reagent in a metal-allyl reaction, which permits the direct construction of enantioenriched β-stereogenic homoallylic esters without preactivation of the pronucleophile or post-reaction modification of the product(e.g., thermal decarboxylation of a 1,3-dicarbonyl). Moreover, the process allows the coupling of a broad range of sterically and electronically diverse electrophiles bearing aryl, heteroaryl and alkenyl derivatives, including the significantly more challenging alkyl-substituted allylic carbonates. The versatility of the ester product is exemplified by a series of functional group manipulations and the development of a concise and efficient enantioselective total synthesis of the natural product,(+)-descurainolide A. Finally, mechanistic studies indicate that the zinc enolate behaves as a soft nucleophile that undergoes outer-sphere alkylation.

关键词： allylic substitution asymmetric catalysis mechanistic studies natural product synthesis Reformatsky reagent

Numerical analysis of high‑speed railway slab tracks using calibrated and validated 3d time‑domain modelling

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Railway Engineering Science 2024年第1期32卷 36-58页

作者： A.F.Esen O.Laghrouche p.K.Woodward d.Medina‑pineda Q.Corbisez J.Y.Shih d.p.Connolly Institute for High‑Speed Rail and System Integration University of LeedsLeeds LS29JTUK Institute for Infrastructure and Environment Heriot-Watt UniversityEdinburgh EH144ASUK Alstom Transport Saint‑OuenFrance Birmingham Centre for Railway Research and Education University of BirminghamBirmingham B152TTUK

Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks,provide safe and smooth rides,and reduce the maintenance *** this paper,the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in *** is then compared to the performance of a ballasted ***,slab and ballasted track models are developed to replicate the full-scale testing of track *** the models are calibrated with the experimental results,the novel slab model is developed and compared against the calibrated slab track *** slab and ballasted track models are then extended to create linear dynamic models,considering the track geodynamics,and simulating train passages at various speeds,for which the Ledsgard documented case was used to validate the *** travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil,considering the issues associated with critical *** train loading methods are discussed,and the most practical approach is retained and ***,correlations are made between the geotechnical parameters of modern high-speed rail and conventional *** is found that considering the same ground condition,the slab track deflections are considerably smaller than those of the ballasted track at high speeds,while they show similar behaviour at low speeds.

关键词： High-speed railways Slab track New ballastless track Ballasted track Critical speeds Finite element modelling Calibration of numerical models

On the functions of astrocyte-mediated neuronal slow inward currents

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Neural Regeneration Research 2024年第12期19卷 2602-2612页

作者： Balázs pál department of physiology Faculty of MedicineUniversity of DebrecenDebrecenHungary

Slow inward currents are known as neuronal excitatory currents mediated by glutamate release and activation of neuronal extra synaptic N-met hyl-d-aspartate receptors with the contribution of *** events are significantly slower than the excitatory postsynaptic *** of slow inward currents are determined by seve ral factors including the mechanisms of astrocytic activation and glutamate release,as well as the diffusion pathways from the release site towards the extra synaptic recepto *** are stimulated by neuronal network activity,which in turn excite neurons,forming an astrocyte-neuron feedback *** as a consequence of brain edema,astrocytic swelling can also induce slow inward currents under pathological *** is a growing body of evidence on the roles of slow inward currents on a single neuron or local network *** events often occur in synchro ny on neurons located in the same astrocytic *** synchronization of neuronal excitability,slow inward currents also set synaptic strength via eliciting timing-dependent synaptic *** addition,slow inward currents are also subject to non-synaptic plasticity triggered by long-la sting stimulation of the excitatory *** note,there might be important regionspecific differences in the roles and actions triggering slow inward *** greater networks,the pathophysiological roles of slow inward currents can be better understood than physiological *** inward currents are identified in the pathophysiological background of autism,as slow inward currents drive early hypersynchrony of the neural *** inward currents are significant contributors to paroxysmal depolarizational shifts/interictal *** events are related to epilepsy,but also found in Alzheimer's disease,parkinson's disease,and stroke,leading to the decline of cognitive *** with features overlapping with slow inward currents(excitatory,N-methyl-dasp

关键词： astrocyte cortical spreading depolarization gliotransmission glutamate neural synchronization NMdA receptor paroxysmal depolarizational shift slow inward current

Temperature and structure measurements of heavy-ion-heated diamond using in situ X-ray diagnostics

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Matter and Radiation at Extremes 2024年第4期9卷 80-89页

作者： J.Lutgert p.Hesselbach M.Schorner V.Bagnoud R.Belikov p.drechsel B.Heuser O.SHumphries p.Katrik B.Lindqvist C.Qu R.Redmer d.Riley G.Schaumann S.Schumacher A.Tauschwitz d.Varentsov K.Weyrich X.Yu B.Zielbauer Zs.Major p.Neumayer d.Kraus Institut fur physik Universitat RostockAlbert-Einstein-Str.2318059 RostockGermany GSI Helmholtzzentrum fur Schwerionenforschung Planckstr.164291 DarmstadtGermany Institut für Angewandte physik Goethe-Universität Frankfurt am MainMax-von-Laue-Str.160438 Frankfurt am MainGermany Institut fur Geowissenschaften Goethe-Universitat Frankfurt am MainAltenhoferallee 160438 Frankfurt am MainGermany Helmholtz-Zentrum dresden-Rossendorf Bautzner Landstr.40001328 DresdenGermany European XFEL GmbH Holzkoppel 422869 SchenefeldGermany Centre for plasma physics School of Mathematics and PhysicsQueen’s University BelfastUniversity RoadBelfast BT71NNUnited Kingdom Institut für Kernphysik Technische Universität DarmstadtSchlossgartenstr.964289 DarmstadtGermany State Key Laboratory of Nuclear physics and Technology Institute of Heavy Ion PhysicsPeking UniversityBeijing 100871China Helmholtz Institut Jena Frobelstieg 307743 JenaGermany

We present in situ measurements of spectrally resolved X-ray scattering and X-ray diffraction from monocrystalline diamond samples heatedwith an intense pulse of heavy *** this way,we determine the samples’heating dynamics and their microscopic and macroscopic structuralintegrity over a timespan of several *** the ratio of elastic to inelastic scattering with state-of-the-art density functionaltheory molecular dynamics simulations allows the inference of average temperatures around 1300 K,in agreement with predictions fromstopping power *** simultaneous diffraction measurements show no hints of any volumetric graphitization of the material,butdo indicate the onset of fracture in the diamond *** experiments pave the way for future studies at the Facility for Antiproton andIon Research,where a substantially increased intensity of the heavy ion beam will be available.

关键词： heated intense structure

Solid-liquid extraction for yttrium recovery using porous polymeric resin(XAd-7) functionalized with d_(2)EHpA

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Journal of Rare Earths 2024年第9期42卷 1764-1773,I0005页

作者： p.A.Martínez-Montoya R.G.Sanchez-Alvarado d.Y.Medina-Velazquez M.L.Carrera-Jota p.Garnica-Chávez A.de J.Morales-Ramirez Higher School of Chemical Engineering and Extractive Industries ESIQIEIPNDepartment of Metallurgical EngineeringUPALM S/NCol.LindavistaGustavo A.Madero Cd.de MéxicoC.P07738Mexico Metropolitan Autonomous University Department of MaterialsBasic Sciences and EngineeringAv.San Pablo No.180Col.Reynosa TamaulipasCd.de MéxicoC.P02200Mexico Center for Research and Technological Innovation CIITECIPNCda.de CECATIs/nSanta CatarinaAzcapotzalcoC.P02250CDMXMexico

The recovery of yttrium is proposed by applying a solid-liquid extraction process using di-2-ethyl hexylphosphoric acid(d2EHpA) as extracting *** extracting agents were supported on a macro porous polymeric resin XAd-7(solid phase).Yttrium ions extraction and discharge tests were performed,firstly from a synthetic aqueous solution of 100 mg/L Y(liquid phase) at 25℃ with *** effects of pH of aqueous solutions bearing yttrium,volume fraction of extracting agents and the solid/liquid(S/L)ratio on the yttrium recovery were *** most favorable conditions for yttrium ions extraction are;20 vol% d_(2)EHpA functionalized resin,pH=1.5 and an S/L ratio of 10 mg/mL The discharge of yttrium ions was done under the same conditions of extraction stage,using a 2 mol/L [H_(2)SO_(4)] as stripping *** to 80% yttrium is extracted,while 75% yttrium is recovered in the striping *** all experiments,the reaction equilibrium is reached after 20 min,and the kinetics for the extraction stage was determined as a second-order ***,experiments were carried out to discharge the yttriumloaded resins,and it has been determined that the best pH value to strip the Y ions is *** tests of extraction and discharge for yttrium ions show that the functionalized resin can work at least five cycles without decreasing its ***,the proposed process was tested in a real solution with Y ions fro m a waste fluorescent la mp powder leached in H_(2)SO_(4),demonstrating the ability to effectively recover yttrium,separating it from various metals from the studied residue.

关键词： Yttrium recovery Rare earth solid-liquid extraction XAd-7 resin Fluorescent lamps recycling Solid-liquid kinetics extraction

Selection of digital fabrication technique in the construction industry--A multi-criteria decision-making approach

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Frontiers of Structural and Civil Engineering 2024年第7期18卷 977-997页

作者： M.p.SALAIMANIMAGUdAM J.JAYApRAKASH department of Structural and Geotechnical Engineering School of Civil EngineeringVellore Institute of TechnologyVellore 632014India

digital fabrication techniques,in recent decades,have provided the basis of a sustainable revolution in the construction ***,selecting the digital fabrication method in terms of manufacturability and functionality requirements is a complex *** paper presents alternatives and criteria for selection of digital fabrication techniques by adopting the multi-criteria decision-making *** alternatives considered in the study are concrete three-dimensional(3d)printing,shotcrete,smart dynamic casting,material intrusion,mesh molding,injection concrete 3d printing,and thin forming *** criteria include formwork utilization,reinforcement incorporation,geometrical complexity,material enhancement,assembly complexity,surface finish,and build *** demonstrates different multi-criteria decision-making techniques,with both subjective and objective weighting *** given ranking is based on the current condition of digital fabrication in the construction *** study reveals that in the selection of digital fabrication techniques,the criteria including reinforcement incorporation,build area,and geometrical complexity play a pivotal role,collectively accounting for nearly 70% of the overall *** the evaluated techniques,concrete 3d printing emerged as the best performer,however the shotcrete and mesh molding techniques in the second and third positions.

关键词： digital fabrication multicriteria decision-making concrete 3d printing

Exploring one material for dual applications:A red-emitting Mg2GeO4:Eu3+ nanophosphor for future generation energy efficient WLEds and dosimetric applications

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Journal of Rare Earths 2024年第10期42卷 1835-1845页

作者： Akshay Arjun G.p.darshan S.C.Sharma H.Nagabhushana d.V.Sunitha H.B.premkumar department of physics Faculty of Mathematical and Physical SciencesM.S.Ramaiah University of Applied Sciences Jain University C.N.R.Rao Centre for Advanced Materials Tumkur University School of Applied Sciences (physics) REVA University

The envisaged design and developme nt of individual mate rials to excavate a broader spectrum of desired properties and offer multiple applications are highly *** this in mind,a series of forsterite-structured Mg2GeO4:Eu3+（1 mol%-9 mol%） nanophosphors was synthesized via a solution combustion method using oxalyl dihydrazide as a *** X-ray diffraction patterns confirm the orthorhombic crystal system with a puma space *** results clearly show irregularly shaped cluster-like structures with aggregation of the *** diffuse reflectance spectra,the optical energy band gap of the Mg2GeO4:Eu3+（1 mol%-9 mol%） nanophosphors was estimated and obtained to be～4.12-4.32 *** photoluminescence emission spectra exhibit intense peaks at ～579,589,610,661,and 707 nm,which are due to characteristic5d0→7F0,5d0→7F1,5do→7F2,5d0→7F3and5d0→7F4transitions of Eu3+ions,*** Commission International de L'Eclairage color coordinates are gradually tuned from pale red（0.5980,0.4012） to a pure red（0.6385,0.3611） *** glow peaks showcase excellent super-linear response at low doses of γ-irradiations,indicating that the prepared phosphor can be used in thermoluminescent personal dosimetry which is a biological tissue *** aforementioned results demonstrate that the prepared Mg2GeO4:Eu3+（1 mol%-9 mol%） nanophosphors are considered an excellent candidate for dual applications,i.e.,red component in future generation white-light-emitting diodes（WLEds） and personal dosimetric applications.

关键词： dosimetry Nanophosphors photoluminescence photometric properties Rare earths Thermoluminescence

detailed seismic zoning of the East Kazakhstan region in the Republic of Kazakhstan

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Geodesy and Geodynamics 2024年第2期15卷 156-165页

作者： Natalya V.Silacheva N.p.Stepanenko O.K.Kurilova A.d.Kudabayeva A.T.danabayeva Institute of Seismology Ministry of Emergency SituationsAlmaty 050060Kazakhstan

Kazakhstan is currently drafting new construction regulations that comply with the major provisions of the *** regulations are created on the basis of seismic zoning maps of various degrees of detail,developed by our Institute of Seismology using a new methodological approach for *** article is about creating the first normative map of the detailed Seismic Zoning on a probabilistic foundation for the Republic of Kazakhstan’s East Kazakhstan *** carried out the probabilistic assessment of seismic hazard using a methodology consistent with the main provisions of Eurocode 8and updated compared with that used in developing maps of Kazakhstan’s General Seismic Zoning and seismic microzoning of *** most thorough and current data accessible for the area under consideration were combined with contemporary analytical *** have been done to not only the databases being used but also the way seismic sources were shown,including active faults *** a scale of 1:1000000,precise seismic zoning maps of the East Kazakhstan region were created for two probabilities of exceedance:10%and 2%in 50 years in terms of peak ground accelerations and macroseismic *** obtained seismic hazard distribution is generally consistent with the General Seismic Zoning of Kazakhstan’s previous ***,because active faults were included and a thoroughly revised catalog was used,there are more pronounced zones of increased danger along the fault in the western part of the *** the west of the territory,acceleration values also increased due to a more accurate consideration of seismotectonic *** maps are the basis for developing new state building regulations of the Republic of Kazakhstan.

关键词： probabilistic seismic hazard assessment detailed seismic zoning peak ground acceleration Microseismical intensity

Single atom Cu-N-C catalysts for the electro-reduction of CO_(2) to CO assessed by rotating ring-disc electrode

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Journal of Energy Chemistry 2024年第1期88卷 169-182,I0004页

作者： S.pérez-Rodríguez M.Gutiérrez-Roa C.Giménez-Rubio d.Ríos-Ruiz p.Arévalo-Cid M.V.Martínez-Huerta A.Zitolo M.J.Lázaro d.Sebastián Instituto de Carboquímica(CSIC) Miguel Luesma Castán 450018 ZaragozaSpain Instituto de Catálisis y petroleoquímica(CSIC) Marie Curie 228049 MadridSpain Synchrotron SOLEIL L’Orme des MerisiersDépartementale 12891190France

The electrochemical CO_(2) reduction reaction(CO_(2)RR) to controllable chemicals is considered as a promising pathway to store intermittent renewable energy. Herein, a set of catalysts based on copper-nitrogendoped carbon xerogel(Cu-N-C) are successfully developed varying the copper amount and the nature of the copper precursor, for the efficient CO_(2)RR. The electrocatalytic performance of Cu-N-C materials is assessed by a rotating ring-disc electrode(RRdE), technique still rarely explored for CO_(2)RR. For comparison, products are also characterized by online gas chromatography in a H-cell. The as-synthesized Cu-NC catalysts are found to be active and highly CO selective at low overpotentials(from -0.6 to -0.8 V ***) in 0.1 M KHCO_(3), while H_(2) from the competitive water reduction appears at larger overpotentials(-0.9 V vs. RHE). The optimum copper acetate-derived catalyst containing Cu-N_(4) moieties exhibits a CO_(2)-to-CO turnover frequency of 997 h^(-1) at -0.9 V vs. RHE with a H_(2)/CO ratio of 1.8. These results demonstrate that RRdE configuration can be used as a feasible approach for identifying electrolysis products from CO_(2)RR.

关键词： Cu-N-C Carbon xerogel Rotating ring disc electrode Carbon dioxide reduction reaction Carbon monoxide