检索结果-南通市图书馆

non-Adiabatic Phonon Dispersion of Metallic Single-Walled Carbon nanotubes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

nano Research 2010年第11期3卷 822-829页

作者： Valentin n.popov Philippe Lambin Faculty of Physics University of SofiaBG-1164 SofiaBulgaria Research Center in Physics of Matter and Radiation Facultés Universitaires Notre Dame de la PaixB-5000 NamurBelgium

non-adiabatic effects can considerably modify the phonon dispersion of low-dimensional metallic ***,these effects are studied for the case of metallic single-walled carbon nanotubes using a perturbative approach within a density-functional-based non-orthogonal tight-binding *** adiabatic phonon dispersion was found to have logarithmic Kohn anomalies at the Brillouin zone center and at two mirror points inside the *** obtained dynamic corrections to the adiabatic phonon dispersion essentially modify and shift the Kohn anomalies as exemplified in the case of nanotube(8,5).Large corrections have the longitudinal optical phonon,which gives rise to the so-called G-band in the Raman spectra,and the carbon hexagon breathing *** results obtained for the G-band for all nanotubes in the diameter range from 0.8 to 3.0 nm can be used for assignment of the high-frequency features in the Raman spectra of nanotube samples.

关键词： nanotube phonons G band tight-binding model

Synthesis and Characterization of Bionanoparticle-Silica Composites and Mesoporous Silica with Large Pores

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

nano Research 2009年第6期2卷 474-483页

作者： Zhongwei niu Saswat Kabisatpathy Jinbo He LAndrew Lee Jianhua Rong Lin Yang Godfrey Sikha Branko n.popov Todd S.Emrick Thomas P.Russell Qian Wang Department of Chemistry and Biochemistry and nanocenter University of South CarolinaColumbiaSC 29208USA Department of Polymer Science and Engineering University of MassachusettsAmherstMA 01003USA Brookhaven national Laboratory UptonNY 11973USA Department of Chemical Engineering University of South CarolinaColumbiaSC 29208USA

A sol-gel process has been developed to incorporate bionanoparticles,such as turnip yellow mosaic virus,cowpea mosaic virus,tobacco mosaic virus,and ferritin into silica,while maintaining the integrity and morphology of the *** structures of the resulting materials were characterized by transmission electron microscopy,small angle X-ray scattering,and n2 adsorption desorption *** results show that the shape and surface morphology of the bionanoparticles are largely preserved after being embedded into *** removal of the bionanoparticles by calcination,mesoporous silica with monodisperse pores,having the shape and surface morphology of the bionanoparticles replicated inside the silica,was produced,.This study is expected to lead to both functional composite materials and mesoporous silica with structurally well-defi ned large pores.

关键词： Mesoporous silica bionanoparticles virus ferritin sol gel

Reduction of friction by normal *** of contact stiffness

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2017年第1期5卷 45-55页

作者： M.popov V.L.popov n.V.popov Berlin University of Technology Berlin 10623 GermanyTomsk Polytechnic University Tomsk 634050 RussiaTomsk State University Tomsk 634050 Russia Berlin University of Technology Berlin 10623 Germany

The present paper is devoted to a theoretical analysis of sliding friction under the influence of oscillations perpendicular to the sliding *** contrast to previous works we analyze the influence of the stiffness of the tribological contact in detail and also consider the case of large oscillation amplitudes at which the contact is lost during a part of the oscillation period,so that the sample starts to 'jump'.It is shown that the macroscopic coefficient of friction is a function of only two dimensionless parameters-a dimensionless sliding velocity and dimensionless oscillation *** function in turn depends on the shape of the contacting *** the present paper,analysis is carried out for two shapes:a flat cylindrical punch and a parabolic *** we consider 'stiff systems',where the contact stiffness is small compared with the stiffness of the *** role of the system stiffness will be studied in more detail in a separate paper.

关键词： sliding friction out-of-plane oscillation contact stiffness coefficient of friction active control of friction

Current self-limitation in a transverse nanosecond discharge with a slotted cathode

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2017年第3期19卷 69-74页

作者： n A ASHURBEKOV K O IMInOV O A popov G S SHAKHSInOV Dagestan State University Faculty of Physics 43a Gadjieva Street Makhachkala 367002 Russia Moscow Power Engineering Institute Krasnokazal'mennaya 14 Moscow 111250 Russia

A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy （few kV） ribbon electron beams. Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr. It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current. A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results. Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed.

关键词： nanosecond discharge electron beams upper current limitation slotted cathode

Dirac operator on the sphere with attached wires

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第4期25卷 335-338页

作者： E n Grishanov D A Eremin D A Ivanov I Yu popov Ogarev Mordovia State University Bolshevistskaya Str. 68 Saransk Russia ITMO University Kroverkskiy pr. 49 St. Petersburg 197101 Russia

An explicitly solvable model for tunnelling of relativistic spinless particles through a sphere is suggested. The model operator is constructed by an operator extensions theory method from the orthogonal sum of the Dirac operators on a semi- axis and on the sphere. The transmission coefficient is obtained. The dependence of the transmission coefficient on the particle energy has a resonant character. One observes pairs of the Breit-Wigner and the Fano resonances. It correlates with the corresponding results for a non-relativistic particle.

关键词： Dirac operator nanostructure tunnelling solvable model

Degenerations of Jordan Algebras and“Marginal”Algebras

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Algebra Colloquium 2021年第2期28卷 281-294页

作者： Ilya Gorshkov Ivan Kaygorodov Yury popov Sobolev Institute of Mathematics NovosibirskRussia Universidade Federal do ABC CMCCSanto AndreBrazil Universidade Estadual de Campinas CampinasBrazil

We describe all degenerations of the variety ■3 of Jordan algebras of dimension three over *** particular,we describe all irreducible components in ■*** every n we define an n-dimensional rigid“marginal”Jordan algebra of level ***,we discuss marginal algebras in associative,alternative,left alternative,non-commutative Jordan,Leibniz and anticommutative cases.

关键词： Jordan algebra degeneration rigid algebra irreducible component marginal algebra

Rodent burrow network dynamics under human-induced landscape transformation from desert to steppe in Kalmykian rangelands

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Integrative Zoology 2019年第4期14卷 410-420页

作者： Elena SURKOVA Sergey popov Andrey TCHABOVSKY A.n.Severtsov Institute of Ecology and Evolution Russian Academy of SciencesMoscowRussia Department of Vertebrate Zoology Lomonosov Moscow State UniversityMoscowRussia

Rodents play an important role in rangelands through the engineering of extensive burrow systems,which provides key habitats for many animal and plant *** have analyzed the long-term variation in the abundance and distribution of rodent burrows in grazing ecosystems of southern Russia(Kalmykia)under the landscape change from desert to steppe caused by the drastic reduction of livestock after the collapse of the USSR in the early *** conducted burrow surveys in the“desert”(1980)and“steppe”(2017)periods on 193-km *** found considerable changes in burrow abundance and distribution,as well as evidence of desert habitat fragmentation and isolation caused by the expansion of tall-grass *** of the open-dwelling diurnal ground squirrel(Spermophilus pygmaeus),the dominant and the keystone species during the“desert”period,almost completely disappeared from the rodent burrow network by 2017,indicating significant habitat *** contrast,the burrows of the folivorous social vole(Microtus socialis)which was rare in the 1980s,became abundant and ubiquitously *** burrow density of the desert-dwelling psammophilous midday gerbil(Meriones meridianus)decreased,while the distances between occupied patches increased,indicating desert habitat fragmentation and loss of population *** of the folivorous tamarisk gerbils(***)were recorded only sporadically in both 1980 and *** observed changes in the rodent burrow network,the key component of grazing ecosystems,correlate with rodent species ecology and can have long-term and important consequences for ecosystem functioning.

关键词： burrows fragmentation grazing impact keystone species rodents

Development of high-coercivity state in melt-spun Fe41Pd41B8Si6P4 ribbons

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2020年第1期39卷 76-83页

作者： Oksana Aleksandrovna Golovnia nina Ivanovna Vlasova Aleksandr Gervasievich popov Vasiliy Semenovich Gaviko Vladimir Vladimirovich popov Jr. Andrey Vladimirovich Protasov Arti Kashyap M.n.Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences EkaterinburgRussia620990 Institute of natural Sciences and Mathematics Ural Federal UniversityEkaterinburgRussia620002 Israel Institute of Metals Technion R&D FoundationTechnion City3200003HaifaIsrael Indian Institute of Technology Mandi KamandMandiHP175005India

The phase transformation and magnetic hysteresis properties of melt-spun Fe41 Pd41 B8 Si6 P4 ribbons subjected to the annealing at temperatures of 500-550℃were studied after holding for 0.1-60.0 h by transmission electron microscopy(TEM),X-ray diffraction(XRD)and thermomagnetic *** additions of P,B and Si to the FePd alloy allowed us to achieve the coercivity of124 kA·m-1,which is 2.6 times higher than that of the melt-spun ribbons of the binary equiatomic FePd *** high-coercivity Fe41Pd41B8 Si6 P4 alloy is nanocrystalline and is composed of the ordered L10-phase grains approximately 40 nm in size and inclusions of the Fe2(P,B)and Pd2(Si,B)*** coercivity kinetics is controlled by the phase transformation which can be divided into three stages:transformation from the bcc structure to nanosized regions of the fee and Fe2 P phases;transformation from the fee to L10 nanosized regions with somewhat different degrees of tetragonality and their ordering;and extensive growth of the weight fraction of L10 phase from the fee nanosized regions.P and B atoms occupy interstitial sites in the iron plane of L10 lattice,thus decreasing its Curie temperature(TC).

关键词： Fe-Pd-P-B-Si Melt spinning L10 nanostructured materials Phase transformation Magnetic measurements

Transient expression of inactive RB in mesenchymal stem cells impairs their adipogenic potential and is associated with hypermethylation of the PPARγ2 promoter

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Genes & Diseases 2022年第1期9卷 165-175页

作者： Mikhail Baryshev nikolai Petrov Vladimir Ryabov Boris popov Institute of Cytology Russian Academy of Sciences St.Petersburg4Tikhoretsky Av.194064St.PetersburgRussia Institute of Microbiology and Virology Riga Stradins UniversityRatsupites 5LV-1067RigaLatvia Developmental Therapeutics Branch National Cancer InstituteNational Institutes of HealthBethesdaMaryland 20892USA

The retinoblastoma gene product(pRb)is a chromatin-associated protein that can either suppress or promote activity of key regulators of tissue-specific *** found that twelve weeks after transfection of the exogenous active(ΔB/X andΔр34)or inactive(ΔS/n)forms of RB into the 10T1/2 mesenchymal stem cells and clonal selection not a single cell line did contain exogenous RB,despite being G-418 ***,the consequences of the transient production of exogenous RB had different effects on the cell ***ΔB/X andΔр34 cells transfected with active form of RB showed elevated levels of inducible adipocyte differentiation(AD).On the contrary,theΔS/n cells transfected with inactive RB mutant were insensitive to induction of AD associated with abolishing of expression of the PPARγ***,the PPARγ2 promoter in undifferentiatedΔS/n cells was hypermethylated,but all except−60 position CpG became mostly demethylated after cells exposure to *** conclude that while transient expression of inactive exogenous RB induces long term epigenetic alterations that prevent adipogenesis,production of active exogenous RBs results in an AD-promoting epigenetic *** results indicate that pRb is involved in the establishment of hereditary epigenetic memory at least by creating a methylation pattern of PPARγ2.

关键词： Adipogenic differentiation DnA methyltransferase 1 Mesenchymal stem cells MSCs RB Retinoblastoma susceptibility gene