Electrochemical performance of tin-based nano-composite electrodes using a vinylene carbonate-containing electrolyte for Li-ion cells

Tin represents a promising material to increase the specific capacity compared to the state of the art graphite anodes in lithium ion cells. The aim of this work is to explain the electrochemical behavior of tin based hydrocarbon nanoparticulate composite electrodes, synthesized by means of a microwave plasma technique without any binder or slurry process. A comprehensive electrochemical character ization shows that adding vinylene carbonate (VC) to the electrolyte improves the electrochemical performance. Electrochemical impedance spectroscopy (EIS) and post mortem investigations of the cycled electrode material by X ray photoelectron spectroscopy (XPS) reveal the formation of a polymeric SEI during the first cycles, being responsible for the improvement. The differential capacity plots of the discharging process show that the lithium richest phase (Li22Sn5) is formed during electrochemical loading. A comprehensive characterization with specially designed electrochemical tests finally dem onstrates the decrease of capacity with increasing temperature. This is due to intensified mechanical stresses and a fresh SEI formation. Due to destruction of the electrode material degradation is also observed with increasing current density. The SEI layer on the surface of the electrodes is confirmed by scanning electron microscopy (SEM) investigations and energy dispersive X ray spectroscopy (EDS) elemental mapping

Anthracosilicosis in the coal mines of Zaječar

Prikazan je problem antrakosilikoze u rudnicima zaječarskog ugljenog basena, Najteži slučajevi antrakosilikoze utvrđeni su u rudniku Vrška Čuka. Analizirana je rudača i jalovina i utvrđene su bogate primjese silicijeva dioksida.The problem of anthracosilicosis in the coal mines of the basin of Zaječar is presented. Most serious cases are observed in the mine Vrška Čuka. The analysis of the ore and rock shows a high Si02 content

Surface Analytical Study Regarding the Solid Electrolyte Interphase Composition of Nanoparticulate SnO₂ Anodes for Li-Ion Batteries

This work presents a comparative surface analytical study on the solid electrolyte interphase (SEI) composition influenced by additives in the electrolyte using nanoparticulate SnO2 as anode active material for lithium ion b a t t e r i e s ( L I B s ) . In pa r t i c u l a r , l i t h i u m b i s (trifluoromethanesulfonyl)imide (LiTFSI) based electrolytes in combination with vinylene carbonate (VC) and 1 fluoroethylene carbonate (FEC) as electrolyte additives are used. The SEI composition of the electrodes is investigated at two different aging stages by means of the complementary X ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF SIMS), providing chemical and molecular information on the topmost surface layers. We are able to show that the additives evolve different influences on the chemical composition of the formed SEI. The use of both additives generally results in an improved cycling stability of the nanoparticulate SnO2 anodes. In consequence, these results open an effective possibility to improve the cycling stability of SnO2 based electrode materials for LIBs by defined tailoring of the electrolyte’s SEI composition

Attitudes of Primary School Teachers Toward Inclusive Education

Background: The aims of our study are related to examining the relevance of teachers' attitudes toward the implementation of inclusive education. In addition, its subject is related to the implications on inclusive education policies, limitations of the existing study along with the recommendations for our future research endeavors. Methods: The research is a cross-sectional study type. The sample included 64 primary school teachers in the lower grades of primary school (grades 1–4), selected by using simple random sampling, in three primary schools on the territory of Belgrade, Serbia in 2021 (26, 17, and 21 primary school teachers). The Questionnaire for Teachers, which was used as a research instrument, was taken from the Master's Thesis Studen Rajke, which was part of the project “Education for the Knowledge Society” at the Institute for Educational Research in Belgrade. Dependent variables measured in the study referred to the attitudes of primary school teachers toward inclusive education. Categorical variables are represented as frequencies and the Chi-square test was used to determine if a distribution of observed frequencies differed from the expected frequencies. Results: One in three teachers (32.8%) thought that inclusion was useful for children with disabilities (29.7%), of them thought that schools did not have the conditions for inclusive education, whereas one in four teachers (25.0%) believed that inclusion was not good. No statistically significant differences were found in the attitudes of professors, when observed in terms of their gender, age and length of service. Conclusion: Investing more resources and time in developing and implementing special education policies can promote successful inclusive education

Improving survey methods in sero-epidemiological studies of injecting drug users: a case example of two cross sectional surveys in Serbia and Montenegro

BACKGROUND: Little is known about the prevalence of HIV or HCV in injecting drug users (IDUs) in Serbia and Montenegro. We measured prevalence of antibodies to HIV (anti-HIV) and hepatitis C virus (anti-HCV), and risk factors for anti-HCV, in community-recruited IDUs in Belgrade and Podgorica, and determined the performance of a parallel rapid HIV testing algorithm. METHODS: Respondent driven sampling and audio-computer assisted survey interviewing (ACASI) methods were employed. Dried blood spots were collected for unlinked anonymous antibody testing. Belgrade IDUs were offered voluntary confidential rapid HIV testing using a parallel testing algorithm, the performance of which was compared with standard laboratory tests. Predictors of anti-HCV positivity and the diagnostic accuracy of the rapid HIV test algorithm were calculated. RESULTS: Overall population prevalence of anti-HIV and anti-HCV in IDUs were 3% and 63% respectively in Belgrade (n = 433) and 0% and 22% in Podgorica (n = 328). Around a quarter of IDUs in each city had injected with used needles and syringes in the last four weeks. In both cities anti-HCV positivity was associated with increasing number of years injecting (eg Belgrade adjusted odds ratio (AOR) 5.6 (95% CI 3.2-9.7) and Podgorica AOR 2.5 (1.3-5.1) for >or= 10 years v 0-4 years), daily injecting (Belgrade AOR 1.6 (1.0-2.7), Podgorica AOR 2.1 (1.3-5.1)), and having ever shared used needles/syringes (Belgrade AOR 2.3 (1.0-5.4), Podgorica AOR 1.9 (1.4-2.6)). Half (47%) of Belgrade participants accepted rapid HIV testing, and there was complete concordance between rapid test results and subsequent confirmatory laboratory tests (sensitivity 100% (95%CI 59%-100%), specificity 100% (95%CI 98%-100%)). CONCLUSION: The combination of community recruitment, ACASI, rapid testing and a linked diagnostic accuracy study provide enhanced methods for conducting blood borne virus sero-prevalence studies in IDUs. The relatively high uptake of rapid testing suggests that introducing this method in community settings could increase the number of people tested in high risk populations. The high prevalence of HCV and relatively high prevalence of injecting risk behaviour indicate that further HIV transmission is likely in IDUs in both cities. Urgent scale up of HIV prevention interventions is needed

Enumeration of labelled quasi-initially connected digraphs

A new class of connected digraphs is introduced - the class of quasi-initially connected digraphs. They are enumerated in the labelled case. Using the apparatus developed for labelled quasi-initially connected digraphs respective results for other classes of labelled connected digraphs were obtained

Ends of semigroups

We define the notion of the partial order of ends of the Cayley graph of a semigroup. We prove that the structure of the ends of a semigroup is invariant under change of finite generating set and at the same time is inherited by subsemigroups and extensions of finite Rees index. We prove an analogue of Hopf's Theorem, stating that a group has 1, 2 or infinitely many ends, for left cancellative semigroups and that the cardinality of the set of ends is invariant in subsemigroups and extension of finite Green index in left cancellative semigroups