735 research outputs found
Some results of cislunar plasma research
The main results of plasma cislunar investigations, carried out during Luna-19 and Luna-22 spacecraft flights by means of dual frequency dispersion interferrometry, are briefly outlined. It is shown that a thin layer of plasma, with a height of several tens of kilometers and a maximum concentration of the order 1,000 electrons/cu cm exists above the solar illuminated lunar surface. A physical model of the formation and existence of such a plasma in cislunar space is proposed, taking into account the influence of local magnetic areas on the moon
The nighttime ionosphere of Mars from Mars-4 and Mars-5 radio occultation dual-frequency measurements
Dual frequency radio sounding of the Martian nighttime ionosphere was carried out during the exits from behind the planet of the Mars-4 spacecraft on February 2, 1974 and the Mars-5 spacecraft on February 18, 1974. In these experiments, the spacecraft transmitter emitted two coherent monochromatic signals in decimeter and centimeter wavelength ranges. At the Earth receiving station, the reduced phase difference (or frequencies) of these signals was measured. The nighttime ionosphere of Mars measured in both cases had a peak electron density of approximately 5 X 1,000/cu cm at an altitude of 110 to 130 km. At the times of spacecraft exit, the solar zenith angles at the point of occultation were 127 deg and 106 deg, respectively. The height profiles of electron concentration were obtained assuming spherical symmetry of the Martian ionosphere
Experimental and theoretical analysis of the upper critical field in FSF trilayers
The upper critical magnetic field H_{c2} in thin-film FSF trilayer spin-valve
cores is studied experimentally and theoretically in geometries perpendicular
and parallel to the heterostructure surface. The series of samples with
variable thicknesses of the bottom and of the top Cu_{41}Ni_{59} F-layers are
prepared in a single run, utilizing a wedge deposition technique. The critical
field H_{c2} is measured in the temperature range K and for magnetic
fields up to 9 Tesla. A transition from oscillatory to reentrant behavior of
the superconducting transition temperature versus F-layers thickness, induced
by an external magnetic field, has been observed for the first time. In order
to properly interpret the experimental data, we develop a quasiclassical
theory, enabling one to evaluate the temperature dependence of the critical
field and the superconducting transition temperature for an arbitrary set of
the system parameters. A fairly good agreement between our experimental data
and theoretical predictions is demonstrated for all samples, using a single set
of fit parameters. This confirms adequacy of the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) physics in determining the unusual
superconducting properties of the studied Cu_{41}Ni_{59}/Nb/Cu_{41}Ni_{59}
spin-valve core trilayers.Comment: 16 pages, 7 figures; published versio
Studying effects of external conditions of electrochemical measurements on the photoelectrochemical properties of semiconductors: cyclic voltammetry, impedance spectroscopy, and Mott – Schottky method
In this paper, the dependences of the semiconductors’ photoelectrochemical properties on the experimental conditions were studied for the solid solution of CdS and ZnS, graphitic carbon nitride, and the platinized carbon nitride. The cyclic voltammograms were obtained under different scan rates. The sample investigations were carried out by two ways, at the constant external voltage and varied amplitudes and at different external voltages and the fixed amplitude. The Mott – Schottky dependences were studied at different frequencies. The basic dependences of the changes in the photoelectrode target characteristics on the experimental condition were found. Some recommendations for the correct comparison of qualitative and quantitative photoelectrochemical data were formulated.https://doi.org/10.15826/elmattech.2023.2.01
Гнездование большого баклана (Phalacrocorax carbo) на техногенных сооружениях в Украине
In Ukraine the Great Cormorant (Phalacrocorax carbo Linnaeus, 1758) uses a rather wide range of habitats for nesting: islands, trees and shrubs, reedbeds and a variety of man-made structures. In general, the strategy of nesting on man-made structures is uncommon both in Ukraine and Europe, and Cormorantsdo this only in the absence of other sites suitable for nesting. Special research onCormorant colonies on technogenic constructions was carried out during the field expeditions by the Research Institute of Biodiversity of Terrestrial and Aquatic Ecosystems of Ukraine in 2002–2003 and 2012–2016. Besides this, we used retrospective and current data from the literature and Internet resources. Most of the field work was carried out by making surveys by boat and on foot. As a result, we found 8 Cormorant colonies on technogenic constructions in Ukraine: gas platforms in the Sea of Azov (near the village Strilkove, Henichesk district of Kherson region); sunken ships – targets for bombing training near the Arabat Spit (these are also known as «ship islands»); electricity pylons of the high-voltage Enerhodar Dnipro Power Line where it crosses the Kakhovka Reservoir; the dock in Yahorlyk Bayk, used in the past as a target for bombing training bombing; artificial island-platforms on Lake Chernine (Kinburn Peninsula); an artificial island on the Sasyk Lagoon (Odessa region); artificial islands, made as navigation markers on the Kremenchuk and Kiev reservoirs. The study found that in most cases the accompanying species was the CaspianGull (Larus cachinnans Pallas, 1811), which actively destroys the Cormorants’ nests and eats their eggs and chicks. The number of nests in the colonies varied greatly (5–30 nests on the navigation marker islands and ca. 2 000–2 300 on the «ship-islands» and gas platforms). This is due, primarily, to the area of the breeding territory. The research found that fierce territorial competition was observed in most of the colonies both with Caspian Gulls and between Cormorants. In addition, we observed anthropogenic interference in the colonies by fishermen and workers conducting routine maintenance work (as happened in the case of electricity pylons and gas platforms). The benefit of this study is that it is the first research in Ukraine conducted at national level onthis type of nesting by Cormorants. Moreover, the study examines the history of emergence of these nesting territories and population dynamics of the Great Cormorant from the time of initial settlement of the breeding sites till the present.Гнездование большого баклана (Phalacrocorax carbo Linnaeus, 1758)на техногенных сооружениях является одним из проявлений его стратегии гнездостроительства, помимо наземной и древесной. В Украине установлены следующие техногенные объекты, служащие гнездовыми территориями для баклана: газовые вышки в Азовском море, затопленные корабли и док – мишени для учебного бомбометания, опоры ЛЭП и рукотворные острова на Киевском и Кременчугском водохранилищах, озерах Сасык и Чернино. В настоящее время существуют шесть из них. В большинстве случаев сопутствующим видом является чайка-хохотунья (Larus cachinnans Pallas, 1811), активно разоряющая гнезда баклана и поедающая яйца и птенцов. Оценена динамика численности баклана с момента заселения объектов и по настоящее время. Антропогенное вмешательство в колониях происходит не только в тех случаях, когда это предписано регламентными эксплуатационными работами (как на опорах ЛЭП и газовых вышках), но и со стороны посещающих гнездовья рыбаков. Ввиду отсутствия гнездопригодных территорий поблизости в колониях наблюдается ощутимая территориальная конкуренция как с чайкой-хохотуньей, так и между бакланами.Гнездование большого баклана (Phalacrocorax carbo Linnaeus, 1758)на техногенных сооружениях является одним из проявлений его стратегии гнездостроительства, помимо наземной и древесной. В Украине установлены следующие техногенные объекты, служащие гнездовыми территориями для баклана: газовые вышки в Азовском море, затопленные корабли и док – мишени для учебного бомбометания, опоры ЛЭП и рукотворные острова на Киевском и Кременчугском водохранилищах, озерах Сасык и Чернино. В настоящее время существуют шесть из них. В большинстве случаев сопутствующим видом является чайка-хохотунья (Larus cachinnans Pallas, 1811), активно разоряющая гнезда баклана и поедающая яйца и птенцов. Оценена динамика численности баклана с момента заселения объектов и по настоящее время. Антропогенное вмешательство в колониях происходит не только в тех случаях, когда это предписано регламентными эксплуатационными работами (как на опорах ЛЭП и газовых вышках), но и со стороны посещающих гнездовья рыбаков. Ввиду отсутствия гнездопригодных территорий поблизости в колониях наблюдается ощутимая территориальная конкуренция как с чайкой-хохотуньей, так и между бакланами
Influence of randomly distributed magnetic nanoparticles on surface superconductivity in Nb films
We report on combined resistance and magnetic measurements in a hybrid
structure (HS) of randomly distributed anisotropic CoPt magnetic nanoparticles
(MN) embedded in a 160 nm Nb thick film. Our resistance measurements exhibited
a sharp increase at the magnetically determined bulk upper-critical fields
Hc2(T). Above these points the resistance curves are rounded, attaining the
normal state value at much higher fields identified as the surface
superconductivity fields Hc3(T). When plotted in reduced temperature units, the
characteristic field lines Hc3(T) of the HS and of a pure Nb film, prepared at
exactly the same conditions, coincide for H10 kOe
they strongly segregate. Interestingly, the characteristic value H=10 kOe is
equal to the saturation field of the MN. The behavior mentioned above is
observed only for the case where the field is normal to the HS, while is absent
when the field is parallel to the film. Our experimental results suggest that
the observed enhancement of surface superconductivity field Hc3(T) is possibly
due to the not uniform local reduction of the external magnetic field by the
dipolar fields of the MN.Comment: to be published in Phys. Rev.
Memory Effect and Triplet Pairing Generation in the Superconducting Exchange Biased Co/CoOx/Cu41Ni59/Nb/Cu41Ni59 Layered Heterostructure
We fabricated a nanolayered hybrid superconductor-ferromagnet spin-valve
structure, the resistive state of which depends on the preceding magnetic field
polarity. The effect is based on a strong exchange bias (about -2 kOe) on a
diluted ferromagnetic copper-nickel alloy and generation of a long range odd in
frequency triplet pairing component. The difference of high and low resistance
states at zero magnetic field is 90% of the normal state resistance for a
transport current of 250 {\mu}A and still around 42% for 10 {\mu}A. Both logic
states of the structure do not require biasing fields or currents in the idle
mode.Comment: 9 pages, 4 figures, Accepted to Applied Physics Letter
Reentrant Superconductivity and Superconducting Critical Temperature Oscillations in F/S/F trilayers of Cu41Ni59/Nb/Cu41Ni59 Grown on Cobalt Oxide
Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers constitute the core
of a superconducting spin valve. The switching effect of the spin valve is
based on interference phenomena occurring due to the proximity effect at the
S/F interfaces. A remarkable effect is only expected if the core structure
exhibits strong critical temperature oscillations, or most favorable, reentrant
superconductivity, when the thickness of the ferromagnetic layer is increased.
The core structure has to be grown on an antiferromagnetic oxide layer (or such
layer to be placed on top) to pin by exchange bias the
magnetization-orientation of one of the ferromagnetic layers. In the present
paper we demonstrate that this is possible, keeping the superconducting
behavior of the core structure undisturbed.Comment: 22 pages, 12 figures, 1 tabl
Scaling behaviour of relaxation dependencies in metaloxide superconductors
Superconducting glass state has been investigated in different types of metaloxide ceramics, Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Ba-Pb-Bi-O, using the highly sensitive SQUID magnetometer. The analysis of long-time relaxation processes of thermoremanent magnetization m(sup trm) (+) = M(sub o) - Slnt displayed scaling dependence of the decay rate S = -dM/dlnt on quantity of trapped magnetic flux M(sub o): 1gs = 31g M(sub o) - observed universal dependence S is approximately M(sup 3) (sub o) seems to one of the features of superconducting glass state in metaloxide ceramics
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