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SnSi nanocrystals of zinc-blende structure in a Si matrix

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Nano Research 2015年第12期8卷 3905-3911页

作者： alexander Tonkikht Andrey Klavsyuk Nikolay Zakharov alexander Saletsky Peter Werner Max Planck Institute of Microstructure Physics Halle(Saale) 06120 Germany Faculty of Physics Moscow State University Moscow 119991 Russian Federation

A zinc-blende （sphalerite） crystallographic structure of SnSi nanocrystals generated by molecular-beam epitaxy is observed by electron microscopy techniques in a Si matrix. Ab initio density-functional modeling reveals a stabilizing effect of the Si matrix, which results in the lowest formation enthalpy of SnSi nanocrystals having the unexpected zinc-blende structure. Such nanocrystals could be applied in Si photonics to function as non-centrosymmetric media for the nonlinear optical process of second harmonic generation.

关键词： epitaxy density functional theory zinc-blende Si-Sn alloy

Improved proper motion determinations for 15 open clusters based on the UCAC4 catalog

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Research in Astronomy and Astrophysics 2016年第7期16卷 39-46页

作者： alexander Kurtenkov Nadezhda Dimitrova alexander Atanasov Teodor D.Aleksiev Department of Astronomy University of Sofia5 James Bourchier Blvd.1164 SofiaBulgaria Institute of Astronomy and National Astronomical Observatory Bulgarian Academy of Sciences72 Tsarigradsko Shose Blvd.1784 SofiaBulgaria Anglo-American School of Sofia 1 Siyanie Str.1138 SofiaBulgaria Geo Milev High School of Mathematics Storgozia5802 PlevenBulgaria Sofia High School of Mathematics 61 Iskar Str.1000 SofiaBulgaria

The proper motions of 15 nearby（d 〈 1 kpc） open clusters（OCs） were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were used. The results significantly differ from the ones presented by Dias et al.（2014）. This could be explained by a different approach in which we take the field star contamination into account. The present work aims to emphasize the importance of applying photometric criteria for the calculation of OC proper motions.

关键词： proper motions Galaxy open clusters and associations general

Statistical Estimation of the Shannon Entropy

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Acta Mathematica Sinica,English Series 2019年第1期35卷 17-46页

作者： alexander BULINSKI Denis DIMITROV Steklov Mathematical Institute of Russian Academy of Sciences and Department of Mathematics and Mechanics Lomonosov Moscow State UniversityMoscow 119234Russia

The behavior of the Kozachenko–Leonenko estimates for the(differential) Shannon entropy is studied when the number of i.i.d. vector-valued observations tends to infinity. The asymptotic unbiasedness and L^2-consistency of the estimates are established. The conditions employed involve the analogues of the Hardy–Littlewood maximal function. It is shown that the results are valid in particular for the entropy estimation of any nondegenerate Gaussian vector.

关键词： Shannon differential entropy Kozachenko-Leonenko estimates Hardy-Littlewood maxi-mal function analogues asymptotic unbiasedness and L^2-consistency Gaussian vectors

How big can a walking fish be?A theoretical inference based on observations on four land-dwelling fish genera of South Vietnam

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Integrative Zoology 2022年第5期17卷 849-878页

作者： alexander N.KUZNETSOV Borissiak Paleontological Institute Russian Academy of SciencesMoscowRussia

Comparative study of terrestrial locomotion of 4ﬁsh genera including Anabas,Channa,Clarias,and Monopterus,was performed in experimental setting with the substrate surface of wet *** special adaptations for terrestrial locomotion were ***ﬁsh uses for propulsion on land what it already ***-shaped Monopterus crawls by body undulations in a serpentine or sidewinding technique,the latter of which was not previously observed beyond *** other 3ﬁsh genera walk by body oscillations using stiff appendages as *** they are located anteriorly,as the serrate operculum in Anabas and the preaxial spine of the pectoralﬁn in Clarias,the propulsion is termed prolocomotor,when posteriorly,as the spiny analﬁn in Channa—*** is the heaviestﬁsh walking out of water in our days,quite comparable in size withﬁrst Devonian tetrapods Acan-thostega and Tulerpeton.A theoretical calculation is suggested for the upper size limit of aﬁsh capable of terrestrial walking without special locomotor *** should be roughly 20 cm in the vertical dimension of the trunk,which is just a little above the known size of Devonian tetrapodomorphﬁshes Panderichthys and *** metalocomotor walking technique of Channa is suggested as the closest extant model for terrestrial locomotion at theﬁsh-tetrapod *** major difference is that the metalocomotor propulsor in Channa is represented by the analﬁn,while in tetrapodomorphs by the pelvicﬁ*** sprawled pelvicﬁns were advantageous in respect of reduced requirement for side-to-side tail swinging.

关键词： ﬁsh-tetrapod transition metalocomotor propulsion prolocomotor propulsion snakehead

Hebbian plasticity:the elusive missing link at the heart of Alzheimer’s disease pathogenesis?

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Neural Regeneration Research 2023年第1期18卷 123-124页

作者： alexander F.Jeans Department of Pharmacology University of OxfordOxfordUK

The amyloid cascade hypothesis of Alzheimer’s pathogenesis:The amyloid cascade hypothesis of Alzheimer’s disease(AD)pathogenesis will shortly celebrate its thirtieth birthday(Hardy and Higgins,1992).Based on abundant genetic and biochemical evidence,it proposes that deposition of the amyloid-β(Aβ)peptide in brain parenchyma is an essential upstream trigger in AD pathogenesis that drives a cascade of events,specifically including the recruitment and pathological hyper-phosphorylation of the micro-tubule-associated protein tau,that culminate in derangement of synaptic function and,eventually,neuronal death.

关键词： pathogenesis Alzheimer eventually

Loss and Damage as an Alternative to Resilience and Vulnerability?Preliminary Reflections on an Emerging Climate Change Adaptation Discourse

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International Journal of Disaster Risk Science 2014年第1期5卷 88-93页

作者： alexander Fekete Patrick Sakdapolrak Risk and Crisis Management Section Cologne University of Applied Sciences50679 CologneGermany Department of Geography University of Bonn53115 BonnGermany

One relatively novel way of assessing the characteristics and limitations of resilience and vulnerability(R&V)is undertaken in this article by investigating a growing alternative paradigm—loss and damage(L&D)*** idea of L&D as an emerging policy may be surprising to many in the disaster risk management community,and so we first outline the origins of this trend,and then explore the potential benefits and pitfalls of adopting *** short article represents our preliminary opinions and observations regarding this reintroduction of a longestablished *** also present results from a very brief peer-group survey on some of the first immediate reactions towards L&D *** this early stage,this article cannot offer a full-fledged analysis,but our reflections may serve as a starting point to encourage further discussion.

关键词： Climate change adaptation Loss and damage Resilience Vulnerability

AN EFFICIENT METHOD FOR MULTIOBJECTIVE OPTIMAL CONTROL AND OPTIMAL CONTROL SUBJECT TO INTEGRAL CONSTRAINTS

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Journal of Computational Mathematics 2010年第4期28卷 517-551页

作者： Ajeet Kumar alexander Vladimirsky Department of Theoretical & Applied Mechanics Cornell University Department of Mathematics Cornell University

We introduce a new and efficient numerical method for multicriterion optimal control and single criterion optimal control under integral constraints. The approach is based on extending the state space to include information on a ＂budget＂ remaining to satisfy each constraint; the augmented Hamilton-Jacobi-Bellman PDE is then solved numerically. The efficiency of our approach hinges on the causality in that PDE, i.e., the monotonicity of characteristic curves in one of the newly added dimensions. A semi-Lagrangian ＂marching＂ method is used to approximate the discontinuous viscosity solution efficiently. We compare this to a recently introduced ＂weighted sum＂ based algorithm for the same problem [25]. We illustrate our method using examples from flight path planning and robotic navigation in the presence of friendly and adversarial observers.

关键词： Optimal control Multiobjective optimization Pareto front Vector dynamic programming Hamilton-Jacobi equation Discontinuous viscosity solution Semi-Lagrangian discretization.

Examples of unbounded homogeneous domains in complex space

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Science China Mathematics 2005年第z1期48卷 248-261页

作者： Michael Eastwood alexander Isaev Department of Pure Mathematics University of Adelaide South Australia 5005AustraliaDepartment of Mathematics The Australian National UniversityCanberraACT 0200Australia

We present several examples of homogeneous domains in complex space that do not have bounded realisations. The domains are equivalent to tubes over affinely homogeneous domains in real space.

关键词： homogeneous unbounded domains.

Analysis of the X-ray emission of OB stars II: B stars

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Research in Astronomy and Astrophysics 2019年第8期19卷 143-150页

作者： Elizaveta Ryspaeva alexander Kholtygin Crimean Astrophysical Observatory NauchnyCrimeaRussia Saint-Petersburg State University Saint-PetersburgRussia Institute of Astronomy Russian Academy of SciencesRussia

This paper is the second part of an investigation into the mechanism for the origin of X-rays in early-type stars. Archival X-ray observations of 25 B stars, obtained by the XMM-Newton satellite, are analysed. We check two hypotheses on the origin of X-ray emission: the Magnetically Confined Wind Shock Model(MCWS) and Pollock’s paradigm. For all studied stars, the mean ratio of the half widths at half maximum to the terminal velocities appears to be R ≈ 0.15-0.20 in contradiction to Pollock’s hypothesis that R ≈ 0.5. We checked three possible consequences of the MCWS model: correlations between the hardness of the X-ray spectra for B stars and terminal wind velocities, mass loss rates and magnetic *** was shown that such correlations are marginal or even absent both for magnetic and non-magnetic B stars.

关键词： stars:early-type stars:spectra:X-ray