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First principles calculation of spin-related quantities for point defect qubit research

npj Computational Materials 2018年第1期4卷 32-44页

作者： Viktor Ivády igor a.abrikosov Adam Gali Department of Physics Chemistry and BiologyLinköping UniversitySE-58183 LinköpingSweden Wigner Research Centre for Physics Hungarian Academy of SciencesPO Box 49Budapest H-1525Hungary Materials Modeling and Development Laboratory National University of Science and Technology‘MISIS’119049 MoscowRussia Department of Atomic Physics Budapest University of Technology and EconomicsBudafokiút 8Budapest H-1111Hungary

Point defect research in semiconductors has gained remarkable new momentum due to the identification of special point defects that can implement qubits and single photon emitters with unique characteristics.Indeed,these implementations are among the few alternatives for quantum technologies that may operate even at room temperature,and therefore discoveries and characterization of novel point defects may highly facilitate future solid state quantum technologies.First principles calculations play an important role in point defect research,since they provide a direct,extended insight into the formation of the defect states.In the last decades,considerable efforts have been made to calculate spin-dependent properties of point defects from first principles.The developed methods have already demonstrated their essential role in quantitative understanding of the physics and application of point defect qubits.Here,we review and discuss accuracy aspects of these novel ab initio methods and report on their most relevant applications for existing point defect qubits in semiconductors.We pay attention to the advantages and limitations of the methodological solutions and highlight additional developments that are expected in the near future.Moreover,we discuss the opportunity of a systematic search for potential point defect qubits,as well as the possible development of predictive spin dynamic simulations facilitated by ab initio calculations of spin-dependent quantities.

关键词： defect quantities principles

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Charge disproportionation and site-selective local magnetic moments in the post-perovskite-type Fe_(2)O_(3) under ultra-high pressures

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npj Computational Materials 2019年第1期5卷 345-351页

作者： Ivan Leonov Gregory Kh.Rozenberg igor a.abrikosov M.N.Miheev Institute of Metal Physics Russian Academy of Sciences620137 YekaterinburgRussia Materials Modeling and Development Laboratory National University of Science and Technology‘MISIS’119049 MoscowRussia School of Physics and Astronomy Tel Aviv University69978 Tel AvivIsrael Department of Physics Chemistry and Biology(IFM)Linköping UniversitySE-58183 LinköpingSweden

The archetypal 3d Mott insulator hematite,Fe_(2)O_(3),is one of the basic oxide components playing an important role in mineralogy of Earth’s lower mantle.Its high pressure-temperature behavior,such as the electronic properties,equation of state,and phase stability is of fundamental importance for understanding the properties and evolution of the Earth’s interior.Here,we study the electronic structure,magnetic state,and lattice stability of Fe_(2)O_(3)at ultra-high pressures using the density functional plus dynamical mean-field theory(DFT+DMFT)approach.In the vicinity of a Mott transition,Fe_(2)O_(3) is found to exhibit a series of complex electronic,magnetic,and structural transformations.In particular,it makes a phase transition to a metal with a post-perovskite crystal structure and site-selective local moments upon compression above 75 GPa.We show that the site-selective phase transition is accompanied by a charge disproportionation of Fe ions,with Fe^(3±δ)and δ~0.05–0.09,implying a complex interplay between electronic correlations and the lattice.Our results suggest that site-selective local moments in Fe_(2)O_(3) persist up to ultra-high pressures of~200–250 GPa,i.e.,sufficiently above the core-mantle boundary.The latter can have important consequences for understanding of the velocity and density anomalies in the Earth’s lower mantle.

关键词： magnetic local high

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Dipolar spin relaxation of divacancy qubits in silicon carbide

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npj Computational Materials 2021年第1期7卷 1974-1984页

作者： Oscar Bulancea-Lindvall Nguyen T.Son igor a.abrikosov Viktor Ivády Department of Physics Chemistry and BiologyLinköping UniversitySE-58183 LinköpingSweden Wigner Research Centre for Physics Hungarian Academy of SciencesPO Box 49H-1525 BudapestHungary Max-Planck-Institut für Physik komplexer Systeme Nöthnitzer Straße 38D-01187 DresdenGermany

Divacancy spins implement qubits with outstanding characteristics and capabilities in an industrial semiconductor host On the other hand,there are still numerous open questions about the physics of these important defects,for instance,spin relaxation has not been thoroughly studied yet.Here,we carry out a theoretical study on environmental spin-induced spin relaxation processes of divacancy qubits in the 4H polytype of silicon carbide(4H-SiC).We reveal all the relevant magnetic field values where the longitudinal spin relaxation time T,drops resonantly due to the coupling to either nuclear spins or electron spins.We quantitatively analyze the dependence of the T,time on the concentration of point defect spins and the applied magnetic field and provide ananalytical expression.We demonstrate that dipolar spin relaxation plays a significant role both in as-grown and ion-implanted samples and it often limits the coherence time of divacancy qubits in 4H-SiC.

关键词： relaxation vacancy resonant

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Finding my way: The role of dirigent proteins in lignin assembly

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Molecular Plant 2024年第2期17卷 230-232页

作者： Dyoni M.Oliveira igor Cesarino Department of Plant Biotechnology and Bioinformatics Ghent University9052 GhentBelgium VIB Center for Plant Systems Biology 9052 GhentBelgium Departamento de Botanica Instituto de BiocienciasUniversidade de Sao PauloRua do Matao277Sao Paulo 05508-090Brazil Synthetic and Systems Biology Center InovaUSPAvenida Professor Lucio Martins Rodrigues370SaoPaulo 05508-020Brazil

Lignin emerged around 450 million years ago in early tracheophytes and played a pivotal role in the colonization of terrestrial ecosystems by plants.This aromatic biopolymer provides mechanical strength to supportive tissues and hydrophobicity to water-transporting vasculature and acts as a physical barrier against herbivores and pathogens(Renault et al.,2019).The deposition of lignin in cell walls for proper cellular functionalization involves several molecular steps,including the tight regulation of tissue-or cell-type-specific expression of lignin biosynthetic genes,the biosynthesis of distinct lignin monomers and their transportation to the apoplast,and the polymerization of monomer radicals to produce tissue-or cell-type-dependent polymers with distinct physico-chemical properties.

关键词： properties. lignin walls

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On the Features of Thermal Convection in a Compressible Gas

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Fluid Dynamics & Materials Processing 2024年第5期20卷 957-974页

作者： igor B.Palymskiy Physics Department Siberian State University of Telecommunications and Information SciencesNovosibirsk City630102Russia Physics Department Siberian State University of Geosystems and TechnologiesNovosibirsk City630108Russia

The fully nonlinear equations of gas dynamics are solved in the framework of a numerical approach in order to study the stability of the steady mode of Rayleigh-Bénard convection in compressible,viscous and heat-conducting gases encapsulated in containers with no-slip boundaries and isothermal top and bottom walls.An initial linear temperature profile is assumed.A map of the possible convective modes is presented assuming the height of the region and the value of the temperature gradient as influential parameters.For a relatively small height,isobaric convection is found to take place,which is taken over by an adiabatic mode when the height exceeds the critical value,or by a super-adiabatic mode in case of a relatively high temperature gradient.In the adiabatic mode,convective flow develops due to adiabatic processes given a stable initial stratification.An analytic formula for the critical height of the region is derived taking into account and neglecting the dependence of the gas viscosity on the temperature.Moreover,an analytic formula is obtained for the upper boundary of the region of applicability of the Boussinesq approximation for incompressible gases.These models for compressible gases are relevant to practical situations such as the study of convective flows in spatially extended gas mixtures when dealing with safety issues related to hydrocarbons stored in gas stations.A dangerous situation arises when the tank is almost empty but some hydrocarbon is left at the bottom of the tank.In the presence of convective flows,the vaporized fuel is mixed with the oxidizer(air)forming a gas-vapor medium.However,if the volumetric concentration of fuel vapor(hydrocarbon)is in the interval between the lower and upper concentration limits of ignition,then the gas-vapor mixture becomes explosive and any accidental spark is sufficient to cause an emergency.

关键词： Rayleigh-Bénard convection gas stable stratification unstable stratification temperature gradient

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Design of Resilient Sensor Networks Balancing Resilience and Efficiency

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International Journal of Disaster Risk Science 2024年第1期15卷 107-115页

作者： Sergey N.Vecherin Kiril D.Ratmanski Luke Hogewood igor Linkov Cold Regions Research and Engineering Laboratory Engineering Research and Development CenterHanoverNH 03755USA Environmental Laboratory Engineering Research and Development CenterVicksburgMS 39180USA

In recent years,the notion of resilience has been developed and applied in many technical areas,becoming exceptionally pertinent to disaster risk science.During a disaster situation,accurate sensing information is the key to efficient recovery efforts.In general,resilience aims to minimize the impact of disruptions to systems through the fast recovery of critical functionality,but resilient design may require redundancy and could increase costs.In this article,we describe a method based on binary linear programming for sensor network design balancing efficiency with resilience.The application of the developed framework is demonstrated for the case of interior building surveillance utilizing infrared sensors in both twoand three-dimensional spaces.The method provides optimal sensor placement,taking into account critical functionality and a desired level of resilience and considering sensor type and availability.The problem formulation,resilience requirements,and application of the optimization algorithm are described in detail.Analysis of sensor locations with and without resilience requirements shows that resilient configuration requires redundancy in number of sensors and their intelligent placement.Both tasks are successfully solved by the described method,which can be applied to strengthen the resilience of sensor networks by design.The proposed methodology is suitable for large-scale optimization problems with many sensors and extensive coverage areas.

关键词： Binary linear programming Optimal sensor placement Redundant networks Resilience and efciency Resilient sensor networks

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Source of metals related to gold occurrences in Cameroon, Central African Belt

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Acta Geochimica 2024年第2期43卷 308-324页

作者： Kevin igor Azeuda Ndonfack Jinlin Zhang Yuling Xie NSamiratou Yaya Emmanuel Archelaus Afanga Basua JCHX Mining Management Co. LtdBeijing 101500People’s Republic of China Institute of Geology Chinese Academy of Geological SciencesBeijing 100037People’s Republic of China School of Civil and Environmental Engineering University of Science and Technology BeijingBeijing 100083People’s Republic of China Department of Earth Science University of BamendaBamendaRepublic of Cameroon

Suites of granitic and metamorphic rocks form a perfect geological environment in which to investigate the source of metals related to gold deposits.In the East Province of Cameroon,the source of metals-related gold(grade~4.6 g/t)that occurs within metamorphic and granitic rocks remains ambiguous.The host rocks were subjected to XRF and ICP-MS whole-rock geochemistry and BSE/EDS mineral analyses to investigate the source(s)of metals related to gold in the Province.Petrographically,chalcopyrite-pyrite and magnetite-ilmenite are the main sulfi des and oxides of granites,respectively.The low-grade metamorphic rocks are sulfi de-rich consisting of arsenopyrite,chalcopyrite,pyrite,and sphalerite,and oxides include magnetite,ilmenite,hematite,and rutile.Cu,Ni,Co,Sb,Sc,and Zn concentrations depleted in high-grade metamorphic rocks and granites compared to low-grade metamorphic rocks.As well,Bi,Cd,Co,Cu,Ni,Sb,V,W,and Zn concentrations decrease with increasing temperatures from low-grade rocks to high-grade rocks and granites.The suite of depleted elements in high-grade rocks and granites is almost identical to those enriched in gold occurrences.We conclude that metals(Bi,Cd,Co,Cu,Ni,Sb,and Zn)related to gold mineralization in the East Province of Cameroon likely originated from metal-rich low-grade metamorphic rocks during prograde metamorphic processes prior to partial melting.

关键词： East Province of Cameroon Metamorphic rocks Granites Oxide–sulﬁdes Metal and gold Geochemistry

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Identifying the stability of housekeeping genes to be used for the quantitative real-time PCR normalization in retinal tissue of streptozotocin-induced diabetic rats

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International Journal of Ophthalmology(English edition) 2024年第5期17卷 794-805页

作者： Muhammad Zulfiqah Sadikan Nurul Alimah Abdul Nasir Mohammad Johari Ibahim igor Iezhitsa Renu Agarwal Department of Pharmacology Faculty of MedicineManipal University College Malaysia(MUCM)Bukit BaruMelaka 75150Malaysia Centre for Neuroscience Research(NeuRon) Faculty of MedicineUniversiti Teknologi MARASungai Buloh CampusSungai BulohSelangor 47000Malaysia Department of Medical Education Faculty of MedicineUniversiti Teknologi MARASungai Buloh CampusSungai BulohSelangor 47000Malaysia Department of Biochemistry and Molecular Medicine Faculty of MedicineUniversiti Teknologi MARASungai Buloh CampusSungai BulohSelangor 47000Malaysia School of Medicine International Medical UniversityBukit JalilKuala Lumpur 57000Malaysia Department of Pharmacology and Bioinformatics Volgograd State Medical UniversityVolgograd 400131Russia

AIM:To investigate the stability of the seven housekeeping genes:beta-actin(ActB),glyceraldehyde-3-phosphate dehydrogenase(GAPDH),18s ribosomal unit 5(18s),cyclophilin A(CycA),hypoxanthine-guanine phosphoribosyl transferase(HPRT),ribosomal protein large P0(36B4)and terminal uridylyl transferase 1(U6)in the diabetic retinal tissue of rat model.METHODS:The expression of these seven genes in rat retinal tissues was determined using real-time quantitative reverse transcription polymerase chain reaction(RT-qPCR)in two groups;normal control rats and streptozotocininduced diabetic rats.The stability analysis of gene expression was investigated using geNorm,NormFinder,BestKeeper,and comparative delta-Ct(ΔCt)algorithms.RESULTS:The 36B4 gene was stably expressed in the retinal tissues of normal control animals;however,it was less stable in diabetic retinas.The 18s gene was expressed consistently in both normal control and diabetic rats’retinal tissue.That this gene was the best reference for data normalisation in RT-qPCR studies that used the retinal tissue of streptozotocin-induced diabetic rats.Furthermore,there was no ideal gene stably expressed for use in all experimental settings.CONCLUSION:Identifying relevant genes is a need for achieving RT-qPCR validity and reliability and must be appropriately achieved based on a specific experimental setting.

关键词： housekeeping genes stability real-time reverse transcription polymerase chain reaction retinal tissue streptozotocin-induced diabetic rats

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Small molecular decoys in Alzheimer's disease

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Neural Regeneration Research 2024年第8期19卷 1658-1659页

作者： Sho Oasa Valentina L.Kouznetsova igor F.Tsigelny Lars Terenius Department of Clinical Neuroscience Center for Molecular MedicineKarolinska InstitutetStockholmSweden San Diego Supercomputer Center University of California San DiegoLa JollaCAUSA Department of Neurosciences University of California San DiegoLa JollaCAUSA Department of Clinical Neuroscience Karolinska University HospitalKarolinska InstitutetStockholmSweden

Recent progress in the treatment of Alzheimer’s disease(AD)using antibodies against amyloid sustains amyloid generation as a key process in AD.Amyloid formation starts with two amyloidbeta(Aβ)molecules interacting(dimer formation)followed by an accelerating build-up of socalled protofibrils,which turn into fibrils,which accumulate in the characteristic plaques.

关键词： Alzheimer decoy Aβ

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Cortical hem signaling center: functions, development, and potential implications for evolution and brain disorders

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Neural Regeneration Research 2025年第4期20卷 1079-1080页

作者： Victor V.Chizhikov igor Y.Iskusnykh Department of Anatomy and Neurobiology University of Tennessee Health Science CenterMemphisTNUSA

Development of the telencephalon relies upon several signaling centers-localized cellular populations that supply secreted factors to pattern the cortical neuroepithelium.One such signaling center is the cortical hem,which arises during embryonic development at the telencephalic dorsal midline,adjacent to the choroid plexus and hippocampal primordium(Figure 1A).While the cortical hem has also been described in reptiles and birds,most of our knowledge about the developmental roles of the cortical hem is derived from the analysis in mice.The cortical hem produces several types of secreted molecules,including wingless-related integration site(Wnt)and bone morphogenetic(Bmp)proteins.The cortical hem is particularly important for the development of the hippocampus,which is involved in learning and memory,and the neocortex,which is the most complex brain region that mediates multiple types of behavior and higher cognitive functions(Mangale et al.,2008;Dal-Valle-Anton and Borrell,2022).

关键词： epithelium Figure center

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