1,383 research outputs found
Effects of charging and electric field on the properties of silicene and germanene
Using first-principles Density Functional Theory calculations, we showed that
electronic and magnetic properties of bare and Ti adatom adsorbed single-layer
silicene and germanene, which are charged or exerted by a perpendicular
electric field are modified to attain new functionalities. In particular, when
exerted by a perpendicular electric field, the symmetry between the planes of
buckled atoms is broken to open a gap at the Dirac points. The occupation of
3d-orbitals of adsorbed Ti atom changes with charging or applied electric field
to induce significant changes of magnetic moment. We predict that neutral
silicene uniformly covered by Ti atoms becomes a half-metal at a specific value
of coverage and hence allows the transport of electrons in one spin direction,
but blocks the opposite direction. These calculated properties, however exhibit
a dependence on the size of the vacuum spacing between periodically repeating
silicene and germanene layers, if they are treated using plane wave basis set
within periodic boundary condition. We clarified the cause of this spurious
dependence and show that it can be eliminated by the use of local orbital basis
set.Comment: Accepted for Journal of Physics: Condensed Matte
Self healing of vacancy defects in single layer graphene and silicene
Self healing mechanisms of vacancy defects in graphene and silicene are
studied using first principles calculations. We investigated host adatom
adsorption, diffusion, vacancy formation and revealed atomistic mechanisms in
the healing of single, double and triple vacancies of single layer graphene and
silicene. Silicon adatom, which is adsorbed to silicene at the top site forms a
dumbbell like structure by pushing one Si atom underneath. The asymmetric
reconstruction of the single vacancy in graphene is induced by the
magnetization through the rebonding of two dangling bonds and acquiring a
significant magnetic moment through remaining unsaturated dangling bond. In
silicene, three two-fold coordinated atoms surrounding the single vacancy
become four-fold coordinated and nonmagnetic through rebonding. The energy
gained through new bond formation becomes the driving force for the
reconstruction. Under the external supply of host atoms, while the vacancy
defects of graphene heal perfectly, Stone-Wales defect can form in the course
of healing of silicene vacancy. The electronic and magnetic properties of
suspended, single layer graphene and silicene are modified by reconstructed
vacancy defects.Comment: Published in PRB: http://prb.aps.org/abstract/PRB/v88/i4/e04544
Economic importance of Gypsophila L., Ankyropetalum Fenzl and Saponaria L. (Caryophyllaceae) taxa of Turkey
Gypsophila L. is the third biggest genus of Caryophyllaceae family in Turkey. The genus has 55 species in the country. 33 species are endemics and total number of the taxa is 58. Ankyropetalum Fenzl is a small genus with 3 species and 1 of them is endemic. Saponaria L. has 20 taxa of 18 species and 10 taxa of them are endemics to Turkey. Turkey is the gene center of all the genera. All of the genera are known as coven, female coven and halva root and developed roots or rhizomes are economically very important. Extract produced from the roots are known as fire extinguisher, gold polishing, cleaner and softener of delicate fabrics and crispness giving to halva. The extracts are often used for making liqueur, herbal cheese, ice cream and some foods. Some taxa are Boron (B) hyperacumulators, so they can be planted and used for destroyed agriculture to control erosion. Gypsophila paniculata L. is very important in horticulture. Gypsophila bicolor, Gypsophila arrostii, Gypsophila perfoliata, Ankyropetalum gypsophiloides and Saponaria officinalis L. are very important because of their saponin contents. In this paper, economic importance of the plants in the light of our observations and literatures was given.Key words: Gypsophila, Ankyropetalum, Saponaria, economy, saponin
Properties and antibacterial activity of MnFe2O4 nanoparticles obtained by pulsed laser ablation in liquid
In this study, MnFe2O4 nanoparticles (NPs) were fabricated via pulsed laser ablation in liquid. Chemical and structural composition, microstructure, magnetic and antibacterial properties were characterized. Spinel was found as the main crystalline phase, while Fe2O3 and Mn2O3 were observed as the major secondary phases, all identified by X-ray diffractometry (XRD). Observation by Transmission Electron Microscopy (TEM) indicated that most of the nanoparticles were spherical in shape and found in agglomerates, most likely because of their magnetic nature. Moreover, Fast Fourier Transform of selective area electron diffraction patterns pointed at the existence of crystalline particles. The coercive field (Hc) and saturation magnetization (Ms) values determined for these NPs were found to increase with decreasing temperature. Their antibacterial properties were evaluated using the viable bacteria counting technique (colony) for MnFe2O4 concentrations of 100 and 300 μg/mL with Bacillus subtilis, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli strains
Economic and Social Impacts by Agricultural Irrigations in Turkey
In this study, we examined the Asartepe dam in Ankara province. We evaluated the economic and social effects of agricultural irrigation and selected main variables are determined as a agricultural usage of water, agricultural production, agricultural productivity, income and environment effects, social-cultural design, migration, economical conditions and etc. A significant portion of the material used in the survey, which was composed of any farming in the area of agriculture to data obtained by the enterprise survey. Survey by interviewing enterprises questionnaire forms have been filled out by going into enterprise. Data for the period from 2015 and 2016 production of agricultural enterprises are collected by questionnaire. In addition to the primary data obtained well as research findings that are previously made on the subject, which has benefited from the secondary data records and published by various organizations. Studies and surveys identified and then a set of selected enterprises are to be implemented by the Simple Random Sampling method (SRS). The information in the questionnaire data entry is made in the MS Office environment. The primary data analysis using SPSS and Eviews entered into the computer program and evaluated in the process of statistical tables are prepared. Keywords: Irrigation, Economic and Social effects, Turke
Thermal Conductivity and Thermoelectric Power of Yb-Substituted Bi-2212 Superconductor
In the present study, Bi2Sr2CaCu2-xYbxO8+y where x = 0.0, 0.05, 0.1 and 0.25, superconductor materials were textured using the Laser Floating Zone technique. After annealing the as-grown materials, they were characterized by thermal conductivity (¿-T), thermoelectric power (S-T), and electrical resistivity (R-T) measurements performed from room temperature down to 20 K. The thermoelectric power is positive in all cases and is found to increase with decreasing temperature, reaching the maximum value (peak) around the samples TC values and dropping rapidly to zero below TC. Electrical resistivity measurements show a slight decrease of TC when Yb substitution is raised. In spite of this effect, TC values are higher than 90 K in all cases. On the other hand, Yb substitution also decreases thermal conductivity, compared with the undoped samples
Effect of Ce substitution on the magnetoresistivity and flux pinning energy of the Bi2Sr2Ca1-x CexCu2O8+δ superconductors
In this study, the effect of Ce doping on the properties of Bi 2Sr2Ca1-x Ce x Cu2O 8+δ ceramic superconductors, with x=0.0, 0.01, 0.05, 0.1, and 0.25, has been investigated. Samples' precursors were prepared using the conventional solid state method and subsequently textured using the Laser Floating Zone technique. The magnetoresistance measurements were studied under various applied magnetic fields. The activation energies, irreversibility fields (H irr ), upper critical fields (H c2) and coherence lengths at 0 K (ξ(0)) were calculated from the resistivity versus temperature (ρ-T) curves, under DC magnetic fields up to 5 T. The thermally activated flux flow model has been applied in order to calculate the flux pinning energies. The results indicated that H c2(0) varied from 416.19 to 115 T and the flux pinning energies varied from 1.46 to 0.042 eV at 0 T. © 2013 Springer Science+Business Media New York.This work is supported by the Research Fund of Çukurova University, Adana, Turkey, under grant contracts No: FEF2011YL27 and FEF2013BAP11. A. Sotelo and M.A. Madre wish to thank the Gobierno de Aragón (Research Group T12), for financial support. M.A. Madre also acknowledges the MINECO-FEDER (Project MAT2011-22719) for funding.Peer Reviewe
Effect of Na substitution and Ag addition on the superconducting properties of Bi-2212 textured materials
The effect of Ag addition on the structural and superconducting properties of Bi2Sr2Ca0.925Na0.075Cu2Oy + x wt% Ag materials with x = 0, 1, 3, and 5 prepared by sol–gel method, followed by directional growth using the laser floating zone (LFZ) technique has been investigated. Powder XRD measurements demonstrate that all samples are composed by nearly single Bi-2212 phase. SEM micrographs and EDX results confirms that Bi-2212 is the major phase with minor amounts of a Bi-free one (Sr, Ca)CuO2 and metallic Ag. According to the magnetic results, Ag does not modify the superconducting critical temperature, Tc, but significantly increases the magnetic hysteresis loop area. The magnetic critical current density is maximum in the 3 wt% Ag containing samples, due to the larger grain clusters found in these samples, reaching 2.1 × 105 A/cm2 at 10 K. Moreover, Ag addition also improves the rods mechanical properties, determined by three point bending tests. The highest bending stress is also reached in the 3 wt% Ag samples
On the solutions of the Schrodinger equation with some molecular potentials: wave function ansatz
Making an ansatz to the wave function, the exact solutions of the %
-dimensional radial Schrodinger equation with some molecular potentials like
pseudoharmonic and modified Kratzer potentials are obtained. The restriction on
the parameters of the given potential, and are also given,
where depends on a linear combination of the angular momentum quantum
number and the spatial dimensions and is a parameter in
the ansatz to the wave function. On inserting D=3, we find that the bound state
eigensolutions recover their standard analytical forms in literature.Comment: 14 page
Exact solutions of the radial Schrodinger equation for some physical potentials
By using an ansatz for the eigenfunction, we have obtained the exact
analytical solutions of the radial Schrodinger equation for the pseudoharmonic
and Kratzer potentials in two dimensions. The energy levels of all the bound
states are easily calculated from this eigenfunction ansatz. The normalized
wavefunctions are also obtained.Comment: 13 page
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