Airy-function electron localization in the oxide superlattices

Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies of the recently fabricated superlattices of lattice-matched perovskite titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential originating from the Coulomb potential of a charged sheet of La atoms. The potential in turn confines the electrons in the vicinity of the sheet, leading to an Airy-function localization of the electron states. Magnetism is suppressed for structures with a single LaTiO3 monolayer, while the bulk antiferromagnetism is recovered in the structures with a thicker LaTiO3, with a narrow transition region separating the magnetic LaTiO3 and the non-magnetic SrTiO3

The Distribution of Minimum of Ratios of Two Random Variables and Its Application in Analysis of Multi-hop Systems

The distributions of random variables are of interest in many areas of science. In this paper, ascertaining on the importance of multi-hop transmission in contemporary wireless communications systems operating over fading channels in the presence of cochannel interference, the probability density functions (PDFs) of minimum of arbitrary number of ratios of Rayleigh, Rician, Nakagami-m, Weibull and α-µ random variables are derived. These expressions can be used to study the outage probability as an important multi-hop system performance measure. Various numerical results complement the proposed mathematical analysis

Ground state, electronic structure and magnetism of LaMnO3

We have calculated the discrete low-energy electronic structure in LaMnO3 originating from the atomic-like states of the strongly correlated 3d4 electronic system occurring in the Mn3+ ion. We take into account very strong intra-atomic correlations, crystal field interactions and the intra-atomic spin-orbit coupling. We calculated magnetic and paramagnetic state of LaMnO3 within the consistent description given by Quantum Atomistic Solid State Theory (QUASST). Our studies indicate that the intra-atomic spin-orbit coupling and the orbital magnetism are indispensable for the physically adequate description of electronic and magnetic properties of LaMnO3. Keywords: 3d oxides, crystal field, spin-orbit coupling, LaMnO3 PACS: 71.70Ej, 75.10DgComment: 5 pages, 2 figures, in RevTex

DEVELOPMENT OF SMES IN AGRIBUSINESS OF VOJVODINA COMMUNES - STATE AND PERSPECTIVES

Agriculture as the economic sector is an important factor of economic development of Serbia and an important part of economic structure. Serbia has agrarian resources (land, climate and water) that are not used enough, and therefore, represent a significant economic potential for further development. Vojvodina is the best-developed economic region of the Republic of Serbia, with dominant role of agricultural production. The main economic potential of Vojvodina development is, among other things, the strengthening and improvement of agriculture in the private sector. Economic potential of agriculture impose the need to analyze this situation in the field of small and medium sized entrepreneurship as the bearer of the future development of agriculture in Vojvodina. Cluster analysis is a method that will determine how to group communes in Vojvodina according to the level of development of small and medium-sized enterprises in the field of agriculture, and thus get an insight into the current state of development of this sector of agriculture, as well as point out the possibilities for the future development of SMEs in agribusiness of Vojvodina.Agricultural production, Small and medium sized enterprises (SMEs), Clusters analysis, Clustering of communes in Vojvodina, Agribusiness, Community/Rural/Urban Development, Public Economics,

Influence of Intra-cell Traffic on the Output Power of Base Station in GSM

In this paper we analyze the influence of intracell traffic in a GSM cell on the base station output power. It is proved that intracell traffic increases this power. If offered traffic is small, the increase of output power is equal to the part of intracell traffic. When the offered traffic and, as the result, call loss increase, the increase of output power becomes less. The results of calculation are verified by the computer simulation of traffic process in the GSM cell. The calculation and the simulation consider the uniform distribution of mobile users in the cell, but the conclusions are of a general nature

First evidence for charge ordering in NaV2_2O5_5 from Raman spectroscopy

We argue on the basis of symmetry selection rules and Raman scattering spectra that NaV$_2$O$_5$ undergoes a charge ordering phase transition at T$_c$=34 K. Such a transition is characterized by the redistribution of the charges at the phase transition and corresponds to the change of the vanadium ions, from uniform V$^{4.5+}$ to two different V$^{4+}$ and V$^{5+}$ states. In the low temperature phase the V$^{4+}$ ions are forming a "zig-zag" ladder structure along the {\bf b}-axis, consistent with the symmetry of the P2/b space group.Comment: to be published in solid state communication

Electronic structure of the substitutional versus interstitial manganese in GaN

Density-functional studies of the electron states in the dilute magnetic semiconductor GaN:Mn reveal major differences for the case of the Mn impurity at the substitutional site Mn_Ga versus the interstitial site Mn_I. The splitting of the two-fold and the three-fold degenerate Mn(d)states in the gap are reversed between the two cases, which is understood in terms of the symmetry-controlled hybridization with the neighboring atoms. In contrast to Mn_Ga, which acts as a deep acceptor, Mn_I acts as a donor, suggesting the formation of Coulomb-stabilized complexes such as (Mn_Ga Mn_I Mn_Ga), where the acceptor level of Mn_Ga is passivated by the Mn_I donor. Formation of such passivated clusters might be the reason for the observed low carrier-doping efficiency of Mn in GaN. Even though the Mn states are located well inside the gap,the wave functions are spread far away from the impurity center. This is caused by the hybridization with the nitrogen atoms, which acquire small magnetic moments aligned with the Mn moment. Implications of the differences in the electronic structure for the optical properties are discussed

Management Measures in Brown Hare Population in Various Habitats in Serbia

Brown hare in Serbia lives in various habitats although the best brown hare habitats are lowland areas and river valleys. Brown hare has successfully adapted to agroecosystems in agricultural areas. In the last two decades in Serbia a number of studies was conducted associated with the analysis of themanagement measures in brown hare population, which recorded some cyclic oscillations in population abundance, density,age structure and exploitationrate. These measures are key elements in management of wildlife population so their implementation should be enforced. Problems related to brown hare population management in Serbia arise because there are neither proper guidelines to determine hare hunting productive areas nor how to define the solvency and capacities of hunting grounds that are not adapted to newly created habitat conditions in certain hunting grounds. Methodology of conducting and defining the number of hare population in various types of hunting grounds does not match given habitat conditions. Taking into account various habitat conditions in hunting grounds of Vojvodina and central Serbia it is very important to define in a correct manner population spring abundance, population density, age structure and exploitation rate for the purpose of sustainable management in hare population

Raman and infrared studies of La_1-ySr_yMn_1-xM_xO_3 (M=Cr, Co, Cu, Zn, Sc or Ga): Oxygen disorder and local vibrational modes

We present results of our study of polarized Raman scattering and infrared reflectivity of rhombohedral ceramic La_1-ySr_yMn_1-xM_xO_3 manganites in the temperature range between 77 and 320K. In our samples, a part of the Mn atoms is substituted by M = Cr, Co, Cu, Zn, Sc, or Ga with x in the range 0 -- 0.1. The hole concentration was kept at the optimal value of about 32% by tuning the Sr content y. We have monitored the distortions of the oxygen sublattice by the presence of broad bands in the Raman spectra, the increase of d.c. resistivity extracted from the infrared reflectivity, and the change of the critical temperature of the ferromagnetic transition. Our results support the idea, that these properties are mainly determined by the radius of the substituent ion, its electronic and magnetic structure playing only a minor role. Furthermore, the Raman spectra exhibit an additional A_g-like high frequency mode attributed to the local breathing vibration of oxygens surrounding the substituent ion. Its frequency and intensity strongly depend on the type of the substituent. In the Co-substituted sample, the mode anomalously softens when going from 300 to 77K. The frequency of the bulk A_{1g} mode depends linearly on the angle of the rhombohedral distortion.Comment: 11 pages, 11 Figures, best-fit values table added, a discussion adde