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Effect of synthesis conditions and surrounding medium on luminescence properties of YVO_4:Eu^(3+) nanopowders

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Journal of Rare Earths 2015年第2期33卷 129-134页

作者： E.V.Golyeva D.V.Tolstikova I.E.Kolesnikov M.D.Mikhailov st.petersburg state Polytechnical university St.Petersburg 195251 Russia Scientific and Technological Institute of Optical Material Science VNTs S.I.Vavilov State Optical InstituteSt.Petersburg 192171 Russia st.petersburg state university St.Petersburg 199034 Russia

Nanocrystalline yttrium vanadate doped with europium ions powders were synthesized via sol-gel method based on decomposition of metal-polymer complex. X-ray diffraction analysis showed that samples had pure tetragonal phase without any impurities. Scanning electron microscopy and static light scattering technique were used to study morphology and size of prepared nanoparticles. Average diameter of the nanoparticles was about 40 nm. The changes in structural and luminescence properties were observed as a function of the first and second calcination temperature. The optimal conditions for synthesis of nanoparticles were determined as Т1=500℃, t1=1 h; Т2=950 ℃, t2=1.5 h. The effect of different media surrounding the nanoparticles on their luminescence properties and lifetime was investigated and discussed in terms of effective refractive index. It was found that the observed lifetime of YVO4：Eu^3＋ 5 at.% nanophosphor was decreased from 0.64 ms in air（nmed=1） to 0.45 ms in chalcogenide glass As39S61（nmed=2.39）.

关键词： nanopowders rare earths luminescence effective refractive index lifetime

Radiation of a TM mode from an open end of a three-layer dielectric capillary

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Chinese Physics B 2024年第7期33卷 311-318页

作者： Sergey NGalyamin Alexandr MAltmark st.petersburg state university 7/9Universitetskayanab.St.Petersburg 199034Russia st.petersburg Electrotechnical university“LETI” 5ProfessoraPopovaSt.Petersburg 197022Russia

Modern trends in beam-driven radiation sources include the interaction of Cherenkov wakefields in open-ended circular waveguides with complicated dielectric linings, with a three-layer dielectric capillary recently proposed to reduce radiation divergence being a representative example [Opt. Lett. 45 5416(2020)]. We present a rigorous approach that allows for an analytical description of the electromagnetic processes that occur when the structure is excited by a single waveguide TM mode. In other words, the corresponding canonical waveguide diffraction problem is solved in a rigorous formulation. This is a continuation of our previous papers which considered simpler cases with a homogeneous or two-layer dielectric filling. Here we use the same analytical approach based on the Wiener–Hopf–Fock technique and deal with the more complicated case of a three-layer dielectric lining. Using the obtained rigorous solution, we discuss the possibility of manipulating the far-field radiation pattern using a third layer made of a low permittivity material.

关键词： diffraction radiation open-ended waveguide Wiener–Hopf technique Cherenkov radiation

Population-specific effects of temperature and photoperiod on development and body mass in Cassida vibex (Coleoptera: Chrysomelidae)

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Insect Science 2023年第6期30卷 1810-1826页

作者： Dmitry Kutcherov Elena B.Lopatina Department of Entomology St.Petersburg State UniversitySt.PetersburgRussia

An interplay of genetic divergence and phenotypic plasticity in shaping geographic variation is increasingly receiving attention in the entomological literature. Two major environmental variables that govern life histories are temperature and photoperiod. studies of thermal and photoperiodic reaction norms help us understand how insect diversity evolved and how insects respond to environmental change. We studied survival, development, and body mass in three geographic populations of the beetle Cassida vibex reared in the laboratory under several combinations of constant temperature (16, 19, 22, 25, and 28 °C) and photoperiod (short-day and long-day). The three collection sites are situated along a climatic gradient and separated by hundreds of kilometers. Each population subtly but significantly differs in the absolute values of survival rate, developmental rate, and body mass as well as in the thermal and photoperiodic plasticity of these traits, but the geographic differences do not form a latitudinal cline. The southernmost population from a relatively warm climate survives worse at low temperatures than the other two, but the overall survival is lowest in the latitudinally intermediate population. Short-day conditions tend to accelerate postembryonic development and increase the slope of the developmental rate–temperature relationship, especially so in the intermediate population, followed by the southernmost population and then by the northernmost population. The latter, which inhabits a harsh climate, has the fastest and most temperature-sensitive development, regardless of photoperiod, and attains the largest body mass among the three populations. The intermediately located and photoperiodically plastic population, which lives in a cool but mild climate, in contrast, has the smallest body size. Hence, although the importance of short-day conditions as a seasonal cue increases poleward, the photoperiodic responses do not always become more pronounced in colder

关键词： adaptation life history photoperiodism plasticity reaction norm temperature

A Model of Irregular Impurity at the Surface of Nanoparticle and Catalytic Activity

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Communications in Theoretical Physics 2012年第7期58卷 55-58页

作者： I.V.Blinova V.V.Gusarov I.Yu.Popov st.petersburg National Research university of Information Technologies Mechanics and OpticsKronverkskiy49St.Petersburg 197101Russia st.petersburg state Technological Institute (technical university) Moskovskiy26St.Petersburg 190013Russia

A problem of nanocatalyst improvement is considered. The existence of irregularities at the surface of nanoparticle leads to the increasing of the surface/volume ratio and, correspondingly, to the improvement of the catalytic activity. But this impurity gives one an additional effect due to the change of the electronic density at the surface. We suggest simple model for the description of this effect. The model allows one to find the discrete spectrum of the Schrdinger operator for nanoparticle. Due to this impurity induced bound states the electron density increases near the surface. It leads to the increase of the catalytic activity of nanoparticles with surface impurities.

关键词： semi-infinite crystal operator spectrum impurity catalytic activity nanoparticle

Impact of drilling waste pollution on land cover in a high subarctic forest-tundra zone

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Pedosphere 2022年第3期32卷 414-425页

作者： Anatoly OPEKUNOV Marina OPEKUNOVA stepan KUKUSHKIN Sergey LISENKOV Institute of Earth Sciences St.Petersburg State UniversitySt.Petersburg 199178(Russia)

Global climate changes can lead to the destruction of the permafrost zone and contribute to the active transfer of pollutants to natural *** can be especially pronounced in the areas of oil and gas production in the *** study aimed to define the landscape components(i.e.,groundwater,soil water,soil,and indicator plant species)of chemical pollution with metals,oil hydrocarbons,and polycyclic aromatic hydrocarbons,from the discharge of drill *** at two sites in the forest-tundra zone of Western Siberia(Russia)were carried out within two years of *** migration was found in peaty-gley heavy loamy soils and iron-illuvial clayey podburs,but lateral migration of different pollutants did not exceed 200 ***,radial migration was practically absent owing to the high buffering capacity of the soil organic horizon and the upward flow of matter in the seasonal melt *** main indicators of drilling waste pollution were high concentrations of Sr,Ba,petroleum hydrocarbons,and Cl^(-)*** the waste disposal sites,the concentration of Ba and Sr in the soil water were 1150 and 1410μg L^(-1),respectively;in groundwater,they reached 721 and 2360μg L^(-1),*** the soil,Ba and Sr accumulated in the peaty horizon(798 and 706 mg kg^(-1),respectively).The concentration of Cl^(-)ions in the soil water at the site of waste discharge was 1912 mg L^(-1),and at a distance of 200 m,it decreased to 77.4 mg L^(-1).The Cl^(-)concentration in the groundwater was lower,and at a distance of 200 m,it was 38.9 mg L^(-1).The highest concentration of petroleum hydrocarbons in the surface layer was found in the peaty-gley soils(up to 2400 mg kg^(-1)).In glandular-illuvial podburs,it was 420 mg kg^(-1).In horizons BH and BC,it was close to the background values(27 and 33 mg kg^(-1),respectively).Alkalinization of soils and water under the influence of drill cuttings led to the death of oligotrophic and acidophilic vegetation at a distanc

关键词： metal petroleum hydrocarbons plant indicator species pollutant migration in soil polycyclic aromatic hydrocarbon

Photoluminescence properties of Eu3+-doped MgAl2O4 nanoparticles in various surrounding media

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Journal of Rare Earths 2019年第8期37卷 806-811,I0001页

作者： I.E.Kolesnikov E.V.Golyeva E.V.Borisov E.Yu Kolesnikov E.Lahderanta A.V.Kurochkin M.D.Mikhailov st.petersburg state university St.PetersburgRussia Lappeenranta university of Technology LUT LappeenrantaFinland Peter the Great st.petersburg Polytechnic university St.PetersburgRussia Scientific and Technological Institute of Optical Material Science VNTs S.I.Vavilov State Optical InstituteSt.PetersburgRussia Volga state university of Technology Yoshkar-OlaRussia

Eu3+-doped MgAl2O4 nanoparticles were prepared by modified Pechini method.X-ray diffraction analysis shows pure tetragonal spinel phase without any *** average size of synthesized nanoparticles was determined to be about 50-60 nm using scanning electron microscopy and static light scattering *** and excitation spectra as well as lifetimes of MgAl2O4:Eu3+ nanophosphors were explored in surrounding media with different refractive *** medium does not affect luminescence bands position,whereas 5D0 lifetime monotonically decreases along with increase of medium refractive *** of surrounding media on radiative and nonradiative decay rates,which were calculated using 4f-4f intensity theory,was studied and *** factor of prepared nanoparticles is defined using both radiative and observed lifetimes.

关键词： Eu3+ Nanoparticles Filling factor Luminescence Lifetime Rare earths

First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry

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Plasma Science and Technology 2024年第10期26卷 49-55页

作者： A.PONOMARENKO A.YASHIN V.GUSEV E.KISELEV G.KURSKIEV V.MINAEV Y.PETROV N.SAKHAROV P.SHCHEGOLEV E.TKACHENKO N.ZHILTSOV Peter the Great st.petersburg Polytechnic university St.Petersburg 195251Russia Ioffe Institute St.Petersburg 194064Russia

The first results of investigation of the turbulence structure using Doppler backscattering(DBS)on the Globus-M2 tokamak are presented.A one-channel DBS system with a variable probing frequency within the 18–26 GHz range was installed to investigate the edge plasma at normalized minor radiiρ=0.9–*** correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH *** analysis was applied to the phase derivative of complex in-phase and quadrature(IQ)signals of the DBS diagnostic as it contains information about the poloidal plasma rotation *** L-mode,the radial correlation length L_(r)is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 *** modelling in a linear local approximation using code GENE indicates that the instability with positive growth rate at the normalized minor radiusρ=0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient(ITG)mode.

关键词： tokamak turbulence Doppler backscattering correlation reflectometry

On the possible orbital motion of Sgr A* in the smooth potential of the Milky Way

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Research in Astronomy and Astrophysics 2020年第12期20卷 383-390页

作者： Igor’I.Nikiforov Angelina V.Veselova st.petersburg state university Universitetskij Prospekt 28Staryj PeterhofSt.Petersburg 198504Russia

The modern accuracy of measurements allows the residual/peculiar(Galactocentric) velocity of the supermassive black hole(SMBH) in our Galaxy, Sgr A*, on the order of several kilometers per *** integrate possible orbits of the SMBH along with the surrounding nuclear stellar cluster(NSC) for a barred model of the Galaxy using modern constraints on the components of the SMBH Galactocentric velocity. Is is shown that the range of oscillations of the SMBH + NSC in a regular Galactic field in the plane of the Galaxy allowed by these constraints strongly depends on the set of central components of the Galactic potential. If the central components are represented only by a bulge/bar, for a point estimate of the SMBH Galactocentric velocity, the oscillation amplitude does not exceed 7 pc in the case that a classical bulge is present and reaches 25 pc if there is no bulge;with SMBH velocity components within the 2σ significance level, the amplitude can reach 15 and 50 pc, respectively. However, when taking into account the nuclear stellar disk(NSD), even in the absence of a bulge, the oscillation amplitude is only 5 pc for the point estimate of the SMBH velocity, and 10 pc for the 2σ significance level. Thus, the possible oscillations of the SMBH + NSC complex from the confirmed components of the Galaxy’s potential are mostly limited by the NSD, and even taking into account the uncertainty of the mass of the latter, the oscillation amplitude can hardly exceed 13 pc = 6′.

关键词： Galaxy:center Galaxy:fundamental parameters Galaxy:kinematics and dynamics

Effect of Crystallization Conditions on Polymorphic Diversity of Malic Acid RS-Racemate

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Transactions of Tianjin university 2013年第2期19卷 86-91页

作者： Isakov A I Kotelnikova E N Kryuchkova L Yu Lorenz H st.petersburg state university St.Petersburg 199034Russia Max Planck Institute for Dynamics of Complex technical Systems Magdeburg 39106Germany

Enantiomers （R （＋） and S（-））, RS-racemate mixture of enantiomers） of malic acid C4H605 have been （double compound） and （R ＋ S） -conglomerate （mechanical investigated by means of X-ray diffractometry and high tern- perature X-ray diffraction method. The RS-racemate was found to be able to form three polymorphic modifications, which we denominated as M1 （monoclinic, space group P21/c）, M2 （monoclinic, space group Cc）, and Tc （triclinic, space group P-l ）, the latter modification having been unknown before. Modification Tc was also described, and its X- ray diffraction characteristics, including interplanar spacings d, hkl indices, unit cell parameters, were defined. In addi- tion, X-ray diffraction characteristics for both reported earlier M1 and M2 monoclinic polymorphic modifications were measured with higher accuracy. The ability of RS-racemate to form one of the above three modifications （MI, M2, and Tc） or their mixtures containing various proportions and combinations of the components （M1 ＋ M2, M1 ＋ Tc, or M2 ＋ Tc） was found to depend on the type of crystallization medium （a melt, aqueous medium, ethanol or acetone solu- tion）, crystallization rate （from 2--3 minutes to 4 months）, and crystallization temperature. Heating S-enantiomer and M1 RS-racemate up to their respective melting points （100 ℃ and 124 ℃, correspondingly） only made them undergo thermal deformations, while heating （R ＋ S） -conglomerate in the temperature range of 96--110 ℃ resulted in its homogenization to form M2 RS-racemate, which, near the melting point （118 ℃）, namely, in the range of 112-116 ℃, was transformed into MI RS-racemate. Keywords： polvmorDhism; racemic, chiral

关键词： polymorphism racemic chiral