THE SPREADING AND DIAGNOSIS OF CANCER OF LARYNX IN THE DOBRICH TOWN AND THE REGION

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Superconducting BSCCO Ceramics as Additive to the Zinc Electrode Mass in the Rechargeable Nickel-Zinc Batteries

The electronic conductivity of the main component of the zinc electrode in the rechargeable zinc-nickel battery – ZnO,  is rather poor and this is the main reason for the electrochemical heterogeneity of the anode mass and the loss of active surface area during charge/discharge cycling with a corresponding negative effect on the electrode characteristics In the present work, the possibility of application of superconductive cuprate Bi-Pb-Sr-Ca-Cu-O (BSCCO) ceramic as a multifunctional conductive additive to the zinc electrode mass is studied. Powder samples of the BSCCO ceramic Bi1,7Pb0,3Sr2Ca2Cu3Ox are produced by two-stage solid-state synthesis and they are physicochemically characterized. The XRD patterns and SEM observation reveal a well crystallized single phase of superconducting 2212 BSCCO system with average crystallite size 5-10 µm. The chemical stability of BSCCO ceramics in highly alkaline medium of the Ni-Zn battery is confirmed by structural and morphological analysis (XRD, SEM and EDX) of the samples before and after prolong exposure (96 h) to 7M KOH. The electrochemical tests are carried out by a specially designed prismatic alkaline Ni-Zn battery cell with conventional sintered type nickel electrodes and pasted zinc electrode with active electrode mass based on ZnO (88 wt.%) and addition of BSCCO powder or acetylene black as conductive additives. The study show that the zinc electrode with BSCCO superconducting ceramic additive exhibits very good cycleability, remarkable capacity stability and much higher discharge capacity at prolong charge/discharge cycling in comparison to the  zinc electrode with the “classic” carbon conductive additive. It is suggested that the addition of BSCCO ceramics improves not only conductivity of the electrode mass and reduces the gas evolution but also stabilizes porosity structure. The results obtained prove the possibility of application of superconducting BSCCO ceramics as a multifunctional additive to the active mass of the zinc electrodes for alkaline battery systems

VIRTUAL LIBRARY OF THE MEDICAL UNIVERSITY OF VARNA - IDEOGENESIS, PRESENCE, AND FUTURE

The Library and Information Service at Prof. Paraskev Stoyanov Medical University of Varna has passed through several stages in its historical development. They results obtained are related with the timely recognition of the necessity of introduction in the Library of the new information technologies. Thus the library staff faces the requirements of the information society of the new millennium. The enthusiastic efforts of the governing body of the library are directed to the permanent improvement of information retrieval in the university medical libraries in Bulgaria, the coordination of their computerization, and the creative enrichment of the forms and methods of information service of the teachers and students. Modern audiovisual means are used along with interactive user's education for independent search in the foreign databases in the library and through Internet. The electronic-mail connections help delivering the documents to the readers in the university departments and clinics after scanning the paper information sources in our library and in other libraries. The electronic library catalogue of books is already accessible through Internet. Our idea of a modern virtual library opened to the future and preserving the rich traditions of our University becomes step-by-step a fascinating reality

Kitaev interactions between j=1/2 moments in honeycomb Na2IrO3 are large and ferromagnetic: insights from ab initio quantum chemistry calculations

Na$_2$IrO$_3$, a honeycomb 5$d^5$ oxide, has been recently identified as a potential realization of the Kitaev spin lattice. The basic feature of this spin model is that for each of the three metal-metal links emerging out of a metal site, the Kitaev interaction connects only spin components perpendicular to the plaquette defined by the magnetic ions and two bridging ligands. The fact that reciprocally orthogonal spin components are coupled along the three different links leads to strong frustration effects and nontrivial physics. While the experiments indicate zigzag antiferromagnetic order in Na$_2$IrO$_3$, the signs and relative strengths of the Kitaev and Heisenberg interactions are still under debate. Herein we report results of ab initio many-body electronic structure calculations and establish that the nearest-neighbor exchange is strongly anisotropic with a dominant ferromagnetic Kitaev part, whereas the Heisenberg contribution is significantly weaker and antiferromagnetic. The calculations further reveal a strong sensitivity to tiny structural details such as the bond angles. In addition to the large spin-orbit interactions, this strong dependence on distortions of the Ir$_2$O$_2$ plaquettes singles out the honeycomb 5$d^5$ oxides as a new playground for the realization of unconventional magnetic ground states and excitations in extended systems.Comment: 13 pages, 2 tables, 3 figures, accepted in NJ

The influence of tuition increase on the desirability of the nursing program at Medical university – Plovdiv

Objective: The aim of the study is to determine how an increase in tuition can change the positive outcome of the sacrifice-gain assessment among nursing students at Medical University – Plovdiv. The study is limited to the negative effect of a higher tuition on the decision of students to drop the program. Methods: The study design is cross-sectional. An anonymous survey was carried out among 160 nursing students in March of 2016. The questionnaire contained items about the social and economic status of the respondent, demographics characteristic and the amount of tuition. Results were analyzed using descriptive statistics and non-parametric analysis. Results: The majority of students consider the current tuition at Medical University- Plovdiv “too high”, and only 23.1% find it “acceptable”. An increase in excess of 30% of the tuition would lead to a drop of 68.8 % or more in the percentage of students willing to continue their education at Medical University-Plovdiv. The percentage of possible transfer students is high in the case not only of freshmen, but of 3rd year students as well. A worrisome fact is the high percentage of respondents (n=26; 16% of the respondents) who, had they been able to turn back time, would not apply to our Nursing program. Conclusion: The results of the survey serve as evidence for the existence of a breaking point, i.e. a level of tuition beyond which students are unwilling to continue their studies

Modeling language learning using specialized Elo ratings

Automatic assessment of the proficiency levels of the learner is a critical part of Intelligent Tutoring Systems. We present methods for assessment in the context of language learning. We use a specialized Elo formula used in conjunction with educational data mining. We simultaneously obtain ratings for the proficiency of the learners and for the difficulty of the linguistic concepts that the learners are trying to master. From the same data we also learn a graph structure representing a domain model capturing the relations among the concepts. This application of Elo provides ratings for learners and concepts which correlate well with subjective proficiency levels of the learners and difficulty levels of the concepts

Iron oxidation state effect on the Mg-Al- Si-O glassy system

Mg-Al-Si-O glassy systems have a great importance in a wide range of industrial applications, specifically as an electrolyte for molten oxide electrolysis processes in steelmaking. Understanding how the iron oxidation state of the raw material (Fe2+/Fe3+) and its corresponding amount influence this glassy system's properties will be the aim of the current work. Iron oxides (as Fe2O3 or Fe3O4) were used to dope Mg-Al-Si-O system obtaining amorphous materials through an unconventional method: Laser Floating Zone (LFZ). Above 8% mol of Fe formation of magnetic phases or iron clusters, were observed in the glass matrix. Samples with Fe2O3 showed a higher crystal concentration, when compared with Fe3O4. The electron paramagnetic resonance measurements show a strong dependence on the iron source (Fe3O4 or Fe2O3). In addition, the magnetization decreases linearly with iron content, independently of iron oxidation state, except for samples with a higher concentration of Fe2O3(15% mol), due to sample crystallization. Moreover, with Fe3O4 as raw material there is an improvement (~250 times) of the electrical conductivity when compared with Fe2O3. The results show that the presence of Fe2+ on the glass influences the electrical conductivity, which could have impact in the efficiency of molten oxide electrolysis process.publishe

Xanthates: Metabolism by Flavoprotein-Containing Monooxygenases and Antimycobacterial Activity.

Ethionamide (ETH) plays a central role in the treatment of tuberculosis in patients resistant to the first-line drugs. The ETH, thioamide, and thiourea class of antituberculosis agents are prodrugs that are oxidatively converted to their active S-oxides by the mycobacterial flavin-dependent monooxygenase (EtaA) of Mycobacterium tuberculosis, thus initiating the chain of reactions that result in inhibition of mycolic acid biosynthesis and cell lysis. As part of a search for new lead candidates, we report here that several xanthates are oxidized by purified EtaA to S-oxide metabolites (perxanthates), which are implicated in the antimycobacterial activity of these compounds. This process, which is analogous to that responsible for activation of ETH, is also catalyzed by human flavoprotein monooxygenase 3. EtaA was not inhibited in a time-dependent manner during the reaction. Xanthates with longer alkyl chains were oxidized more efficiently. EtaA oxidized octyl-xanthate (Km = 5 µM; Vmax = 1.023 nmolP/min; kcat = 5.2 molP/min/molE) more efficiently than ETH (194 µM; 1.46 nmolP/min; 7.73 nmolP/min/molE, respectively). Furthermore, the in vitro antimycobacterial activity of four xanthates against M. tuberculosis H37Hv was higher (minimum inhibitory concentration of around 1 µM) than that of ETH (12 µM)

Phase formation and catalytic activity of Cu-Co-spinel catalyst deposited on Al/Si/Mg -support

The paper is devoted to Cu-Co oxide catalysts deposited on a commercially available high-temperature support containing aluminum, magnesium and silicon, calcined at different temperatures: 350, 450, 550, 650 and 750 o С. The samples are prepared by impregnation with aqueous solutions of Cu and Co nitrates. The catalysts are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), and BET method. Chemical analysis of the samples is also carried out. The phase formation at different preparation temperatures and the catalytic activity of copper cobaltite in the reaction of CO oxidation with oxygen at two space velocities (20 000 and 100 000 h -1 ) are investigated. The stability of the specimens to catalytic poisons at the same space velocities is studied. It is established that the most promising catalysts regarding the catalytic activity and stability to poisoning with SO2 are the catalysts calcined in the range 350 -550 o С. At these temperatures a Cu-Co oxide spinel -like phase is formed. These results give us the reason to suppose a possible implementation of the high-temperature support in the preparation of catalysts for the purification of toxic emissions of gaseous fluids in the practice