Study on the dependence of the critical temperature Tc on pressure in YBa2Cu3O6+x

In the present study experimental data available in the literature have been employed to investigate behavior of the critical temperature Tc as a function of the pressure P, in the YBa2Cu3O6+x high temperature superconductor (HTSC). We estimated the maximal critical temperature Tc,max(P) which can be achieved in this material under pressure applied at temperatures low enough to prevent oxygen reordering. We found that it approximately equals to 114K corresponding to x ≈ 0.77

Impact of oxygen disorder on Tc supression in Zn dopedreba2Cu3O6+x superocnductors

Conducting properties of REBa2Cu3O6+x(RE123) type high Tc superconductors (RE=Y, 4f elements) are highly sensitive to the oxygen order in the oxygen deficient CuOx planes which can be disrupted by doping with different metals,thus leading to a change of the superconducting transition temperature Tc. In this article we shall employ a simple theoretical model of charge transfer to studyhow Tc(x) dependence is affected by the increase of oxygen disorder in the CuOx planes, which is displayed in reduced average CuO chain length, lav. The results indicate that though the increased oxygen disorder can produce significant decrease in Tc, it cannot be the only factor responsible forTc reduction in Zn doped RE123 superconductors

Cvm study of charge transfer in YBa2Cu3O6+x material

The number of positive holes transferred from the CuOx basal planes to the superconducting CuO2 planes of YBa2Cu3O6+x material was calculated as a function of oxygen content x, by the use of numerical cluster variation method (CVM). The calculations were performed for the set of three different temperatures and for the different values of the parameter ξl which represents the ratio of the number m of divalent oxygen ions in the chain fragment and the total number l of oxygen ions in the chain fragment. The obtained hole count versus x dependence showed no plateau behavior for low temperatures (t=0.25 and t=0.35) while for t=0.45 indication of plateau behavior is present.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Thermally Induced Structural Transformations of Fe2O3 Nanoparticles Embedded in a Silica Matrix

XXV Konferencija Srpskog kristalografskog društva : Bajina Bašta, 2018

Crystallization of Fe2O3 and Gd2Si2O7 in Fe2O3/Gd2O3/SiO2 composite system

XXIV Konferencija Srpskog kristalografskog društva : Vršac, 2017

Uticaj inokulacije i đubrenja na efektivnost azotofiksacije kod pasulja

The legume family is comprised of a highly diverse set of plant species essential to animal and human nutrition. The introduction of effective strains of nodule bacteria during bean sowing increases nitrogen fixation and enables these plant species to be grown even on less fertile soils. This paper has studied the effects of inoculation and fertilization on nitrogen fixation parameters in the bean variety Belko. Sowing was done by hand and the seeds were inoculated using the microbiological fertilizer NS-Nitragin which contained a mixture of Rhizobium leguminosarum bv. Phaseoli strains specific to bean as a crop species. Both the bean genotype and NS-Nitragin fertilizer used originate from the Institute. Plant dry matter mass and nitrogen content were determined at flowering, while grain dry matter mass per plant, number of pods formed, and grain number per pod were measured at physiological maturity. The basic agrochemical soil analyses were performed just before sowing, at flowering and at physiological maturity. Plant nitrogen was determined according to Kjeldahl. The trial was established at the Rimski Šančevi Experiment Field and the trial treatments were as follows 1) 0 kg/ha + HR + 50 kg/ha N every three years; 2) 50 kg/ha + HR + 50 kg/ha N every three years; 3) 100 kg/ha + HR + 50 kg/ha N every three years; 4) 50 kg/ha + HR + 50 kg/ha N every three years; 5) 200 kg/ha + HR + 50 kg/ha N every three years; 6) 250 kg/ha + HR + 50 kg/ha N every three years; 7) 0 kg/ha; 8) 100 kg/ha; and 9) 200 kg/ha. No NPK mineral fertilizers were incorporated and the phosphorus and potassium rates were the same (80 kg/ha P2O5 and K2O) in all of the treatments. In treatments 1 through 6 harvest residues (HR) were incorporated by plowing under, and every three years 50 kg/ha N were added after wheat. In treatments 7, 8 and 9 harvest residues were removed. Each treatment consisted of an inoculated and a noninoculated version. The study results showed that inoculation had a positive effect on the symbiotic association parameters concerned, i.e. the plant length, dry matter mass, pod number per plant, grain number per pod and plant nitrogen content of the inoculated plants from all of the treatments were on average greater than those of the noninoculated ones. The different fertilization treatments had different effects on the effectiveness of the symbiotic association as well. The amount of nitrogen fixed ranged from 13.68 to 68.97 kg N/ha, averaging 23.31 kg N/ha. No nitrogen fixation occurred in treatments 5 and 9.U radu je ispitan uticaj inokulacije i đubrenja na parametre azotofiksacije kod sorte pasulja Belko. Ogled je izveden na oglednim poljima Naučnog instituta za ratarstvo i povrtarstvo. Inokulacija semena je izvršena sa mikrobiološkim đubrivom NS-Nitraginom za pasulj. Genotip pasulja Belko i NS-Nitragin poreklom su iz Instituta. U fazi cvetanja i u fazi fiziološke zrelosti urađena je i osnovna agrohemijska analiza zemljišta. U obe faze analizirana je masa biljke (nadzemni deo, koren i kvržice), sadržaj azota u biljci, masa zrna po biljci, broj formiranih mahuna i broj zrna po mahuni. Inokulacija je uticala na povećanje sadržaja humusa i sadržaj ukupanog azota u zemljištu u većini kombinacija đubrenja. U proseku na svim varijantama đubrenja kod inokulisanih biljaka veća je masa suve materije biljke (korena nadzemnog dela i zrna), broj mahuna po biljci, broj zrna po mahuni i sadržaj azota u biljci

The dependence of critical temperature on oxygen concentration in YBa2Cu3O6+x in terms of the fragmented chain model

An extended ASYNNNI model, that beside nearest-neighbour and next-nearest neighbour O-O interactions in the basal plane also includes interactions between the three nearest oxygen atoms, is used to describe the statistics of CuO chain fragmentation and to calculate doping and T (c) in YBa2Cu3O6+x . Calculations were made by the Monte Carlo method employing the recently proposed charge transfer model that assumes only chains whose length is equal to, or exceeds, a characteristic (critical) length, l (cr) , can provide holes to the layers and contribute to doping p. The obtained p(x) is then combined with a universal T (c) versus p relation to yield T (c) (x) characteristics that correlate remarkably with those reported in recent experiments. The best coordination between theoretical and experimental T (c) (x) characteristics has been achieved for l (cr) = 2, implying that only isolated basal plane oxygen atoms (trivial chains) do not contribute holes to CuO2 layers

Mikrobiološka aktivnost - pokazatelj plodnosti i degradacije zemljišta

U zemljištu su u velikom broju zastupljene sve do sada poznate sistematske grupe mikroorganizama (bakterije, gljive, alge, protozoe, virusi). U jednom gramu zemljišta u prošeku se nalazi oko milijardu bakterija, stotine hiljada gljiva, stotine algi i desetine protozoa. Biomasa mikroorganizama iznosi 0,5 do 5 tona po hektaru oraničnog sloja plodnog zemljišta a prema rezultatima Zavjagincev (1994), sveza biomasa mikrobiološkog porekla može da dostigne i do 20 tona po hektaru. Mikroorganizmi čine veoma funkcionalne mikrobiocenoze koje su prilagođene uslovima u zemljištu i zajedno sa florom i faunom daju zemljištu svojstva živog organizama

Internal Quality Control as an Important Part of Radiological Analysis of Environmental Samples Using Semiconductor HPGe Spectrometry

Ugalj kao fosilno gorivo sadrži brojne prirodne radioaktivne izotope koji pripadaju uranovom i torijumovom nizu, kao i 40K. Najviše se koristi u industriji, kao i u proizvodnji energije. Problem u vezi sa proizvodnjom energije iz uglja je takozvani „energetski otpad“, kao što su pepeo i šljaka, koji predstavljaju nesagorivi i nesagoreli ostatak pri sagorevanja uglja. Ako se pepeo i šljaka odlažu u životnu sredinu, može doći do povećanja i/ili preraspodele prirodnog sadržaja radionuklida. Da bi se utvrdio potencijalni uticaj „energetskog otpada“ na životnu sredinu, uzorci uglja, pepela i šljake iz termoelektrana „Nikola Tesla“ i „Kolubara“ mereni su poluprovodničkim HPGe spektrometrom u Laboratoriji za nuklearnu i plazmu fiziku Instituta „Vinča“. Kao rezultat ovih merenja, dobijene su koncentracije prirodnih radionuklida i veštačkog radionuklida 137Cs kao, što je prikazano u ranije objavljenim radovima. Prikazani rezultati su u saglasnosti sa istraživanjima sprovedenim širom sveta. Da bi se obezbedila tačnost i preciznost (pouzdanost) dobijenih rezultata merenja, u okviru Laboratorije uspostavljen je program kontrole kvaliteta (QC) i osiguranja kvaliteta (QA). Interna kontrola obuhvata proveru karakteristika poluprovodničkog HPGe spektrometra koji se koristi za merenje svih analiziranih uzoraka. Tačkasti izvori 60Co i 137Cs se koriste kao kontrolni izvori za proveru položaja pika, ukupne površine ispod pika, FWHM (puna širina na polovini maksimuma pika), FWTM (puna širina na desetini maksimuma pika) i odnos FWHM/FWTM. Pored navedenih karakteristika, redovno se kontroliše i ukupni odbroj prirodnog fona. Svaka od navedenih karakteristika može ukazati na neku nepravilnost u radu detektorskog sistema. Cilj ovograda je da se prikažu kontrolne karte ispitivanih karakteristika poluprovodničkog HPGe spektrometra korišćenog za merenje uzoraka uglja, pepela i šljake. Dobijene kontrolne karte predstavljaju važan alat na osnovu kojeg se analizira dugoročna stabilnost spektrometraeir daughter products, as well as 40K. It is widely used in industry as well as in energy pro-duction. The problems associated with the production of energy from coal is the so-called “energy waste”, such as ash and slag, which are incombustible and unburnt residue from combustion of coal. If ash and slag are released into the environment an increase and/or redistribution of natural radio-nuclide content can occur. To determine the potential impact of “energy waste” on the environment, samples of coal, ash, and slag from thermal power plant "Nikola Tesla" and "Kolubara" were meas-ured with a semiconductor HPGe spectrometer. Results of activity concentration of natural radionu-clides and artificial 137Cs in coal, slag and ash are presented in few previously published papers and obtained values are in accordance with similar worldwide investigations. o ensure the accuracy and precision (reliability) ofthe obtained measurement results, quality control (QC) and quality assurance (QA) program were established. Internal control includes check-ing of the characteristics of HPGe spectrometer used for measurement of all analysed samples. Point sources of 60Co and 137Cs are used as control sources for checking following characteristics: peak positions, net peak area, FWHMs (Full Width at Half Maximum), FWTMs (Full Width at Tenth Max-imum) and FWHM/FWTM ratios. In addition to the mentioned characteristics, the counting of back-ground is also regularly controlled. Each of the mentioned characteristics may indicate some irreg-ularity in the operation of the detector system and thus could influence reliability of performed activ-ity concentration measurements.The paper presents the control charts of the examined characteristics of the HPGe spectrometer used for measurements of coal, ash and slag samples. The obtained control charts indicate the long-term stability of the spectrometer and hence confirm accuracy and precision of measurement results.36. Međunarodni kongres o procesnoj industriji - PROCESING ′23 : zbornik radova ; 1-2. jun, Šaba

Possible role of oxygen monomers reordering in the photoinduced charge transfer in RBa2Cu3O6+x material

The model of photoassisted oxygen ordering assumes that the enhancement of the conducting properties of RBa2Cu3O6+x material during the light illumination, is the consequence of the CuOx plane oxygen atoms reordering into long chain fragments, which are known to be better hole dopants than the short ones. Some experimental results suggest that this process is performed mainly through the reaccomodation of the oxygen monomer units (isolated oxygen ions). In the present work concentration of oxygen monomers in the CuOx planes, which is assumed to be equal to the concentration of holes transferred out of the chain planes during the light illumination, is calculated as a function of oxygen content x, and delta T-c (photoinduced enhancement of the superconducting critical temperature T-c) was estimated for different oxygen concentrations. Numerically found values of the (delta T-c, are shown to be in good agreement with experimental findings. (C) 2011 Elsevier Ltd. All rights reserved