Chemical composition and screening of the antimicrobial and antioxidative activity of extracts of Stachys species

GC and GC/MS analyses of the diethyl ether and ethyl acetate extracts obtained from the aerial parts of Stachys germanica subsp. heldreichii (Boiss) Hayek, Stachys iva Griseb., Stachys plumosa Griseb. and Stachys scardica Griseb., Balkan peninsula endemics, were performed. One hundred and seventy-nine constituents, accounting for 88.8–98.1% of the total composition of the extracts, were identified. The common feature of the diethyl ether extracts was the high content of terpenoids and fatty acid-derived compounds, while the common feature of the ethyl acetate extracts was the prevalence of fatty acid-derived compounds. A disk diffusion method was used for the evaluation of the antimicrobial activities of the extracts against a panel of microorganisms (bacteria: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Salmonella enteritidis; fungi: Aspergillus niger and Candida albicans). The total antioxidant capacity of the extracts was evaluated by the phosphomolybdenum method. The preliminary bioassay results indicated that the diethyl ether extract of S. plumosa could be a possible source of antioxidant and antimicrobial compounds

Phytomedical investigation of Najas minor All. in the view of the chemical constituents

Plants are an abundant natural source of effective antibiotic compounds. Phytomedical investigations of certain plants haven’t still been conducted. One of them is Najas minor (N. minor), an aquatic plant with confirmed allelopathy. Research conducted in this study showed the influence of water and ethyl acetate extracts of N. minor on microorganisms, in the view of chemical profiling of volatile constituents and the concentrations of total phenols, flavonoids and tannins. Antimicrobial activity was defined by determining minimum inhibitory and minimum microbicidal concentrations using microdilution method. Influence on bacterial biofilm formation was performed by tissue culture plate method. The total phenolics, flavonoids and condensed tannins were determined by Folin-Ciocalteu, aluminum chloride and butanol-HCl colorimetric methods. Chemical profiling of volatile constituents was investigated by GC and GC-MS. Water extract didn't have antimicrobial activity below 5000 µg/mL. Ethyl acetate extract has shown strong antimicrobial activity on G+ bacteria - Staphylococcus aureus PMFKGB12 and Bacillus subtilis (MIC < 78.13 µg/mL). The best antibiofilm activity was obtained on Escherichia coli ATCC25922 (BIC50 at 719 µg/mL). Water extract had higher yield. Ethyl acetate extract had a significantly greater amount of total phenolics, flavonoids and tannins. As major constituent hexahydrofarnesyl acetone was identified. The ethyl acetate extract effected only G+ bacteria, but the biofilm formation of G-bacteria was suppressed. There was a connection between those in vivo and in vitro effects against pathogenic bacterial biofilm formation. All of this points to a so far unexplored potential of N. minor

What is needed to develop critical thinking in schools?

Starting with the fact that school education has failed to become education for critical thinking and that one of the reasons for that could be in how education for critical thinking is conceptualised, this paper presents: (1) an analysis of the predominant approach to education for critical thinking through the implementation of special programs and methods, and (2) an attempt to establish different approaches to education for critical thinking. The overview and analysis of understanding education for developing critical thinking as the implementation of special programs reveal that it is perceived as a decontextualised activity, reduced to practicing individual intellectual skills. Foundations for a different approach, which could be characterised as the ‘education for critical competencies’, are found in ideas of critical pedagogy and open curriculum theory. This approach differs from the predominant approach in terms of how the nature and purpose of critical thinking and education for critical thinking are understood. In the approach of education for critical competencies, it is not sufficient to introduce special programs and methods for the development of critical thinking to the existing educational system. This approach emphasises the need to question and reconstruct the status, role, and power of pupils and teachers in the teaching process, but also in the process of curriculum development

Why do teaching techniques in our school lack in diversity?

U prilogu se problematizuje pitanje zašto metode u nastavi u našoj sredini nisu dovoljno raznovrsne. Okvir problematizovanja čine različita naučna saznanja koja upućuju na neophodnost raznovrsnih metoda i tehnika rada u nastavi, reformski proces obrazovanja u Srbiji započet početkom dvehiljadite godine, kao i neki empirijski uvidi o vrstama i načinu korišćenja metoda u nastavi. Najnoviji radovi o metodama nastave, s jedne, i o profesiji nastavnik, s druge strane, ukazuju ne samo na nužnost korišćenja različitih metoda već i na potrebu da nastavnik razvija i u praksi istražuje odgovarajući metodski postupak. U prilogu razmatramo koliko je započeti reformski proces obezbedio uslove za autonomnu ulogu nastavnika u kreiranju obrazovanja različitim metodama i koje još obrazovne i normativne okolnosti imaju uticaja na ovu autonomiju nastavnika u našoj sredini. Problematizujući ovo pitanje zaključile smo da je mnogo više faktora koji ograničavaju profesionalnu autonomiju nastavnika i stavljaju ga pred suprotstavljene profesionalne zahteve od onih koji mu otvaraju prostor za autonomno oblikovanje i razvijanje nastave.The paper discusses the issue of lack in diversity of teaching techniques in our school. The framework for consideration includes different scientific findings which stress the importance of using varied techniques and methodology in teaching, the process of reforming education in Serbia, and some empirical insights on different teaching techniques and the modes of their usage in the classroom. The latest research on the types and modes of usage of teaching techniques, on the one hand, and on teacher profession, on the other, indicate not only the necessity of using different techniques, but also to the need for the teacher to develop and practically explore the possibilities of teaching procedures. This paper is an attempt to analyze to what extent the ongoing reform process provides conditions for teacher autonomy in fostering education by varied teaching techniques and which educational and normative factors affect teacher autonomy in our society. Having considered the issue we concluded that there are many more factors that limit professional autonomy of teachers and confront them with competing professional demands than those which open space for autonomous design and development of teaching

Analysis of the motion and stability of the holonomic mechanical system in the arbitrary force field

U cilju dobijanja uvida u rad mašine pre njene montaže i proizvodnje, kao i dobijanja dobre analize, ovaj rad predstavlja detaljna rešenja specifičnog problema iz oblasti analitičke mehanike. Pored numeričkih postupaka u radu, izvršen je i pregled teorijskih osnova. Razne vrste analiza su vrlo česte u mašinskom inženjerstvu, zbog mogućnosti aproksimacije složenih mašina. Za predloženi sistem date su Lagranžove jednačine prve vrste, kovarijantne i kontravarijantne jednačine, Hamiltonove jednačine, generalisane koordinate, kao i uvid u Kulonovu silu trenja. Takođe, rešeni su i uslovi statičke ravnoteže uz pomoć numeričkih i grafičkih postupaka - presekom dve krive. Konačno, razmatrana je i stabilnost kretanja poremećenog i neporemećenog kretanja.In order to give an insight into the work of the machine before the production and assembly and to obtain good analysis, this paper presents detailed solutions to the specific problem occured in the field of analytical mechanics. In addition to numerical procedures in the paper, a review of the theoretical foundations was made.Various types of analysis are very common in mechanical engineering, due to the possibility of an approximation of complex machines. For the proposed system, Lagrange's equations of the first kind, covariant and contravariant equations, Hamiltons equations and the generalized coordinates, as well as insight in Coulumb friction force are provided.Also, the conditions of static equilibrium are solved numerically and using intersection of the two curves. Finally, stability of motion for the disturbed and undisturbed system was investigated

Analysis of the motion and stability of the holonomic mechanical system in the arbitrary force field

U cilju dobijanja uvida u rad mašine pre njene montaže i proizvodnje, kao i dobijanja dobre analize, ovaj rad predstavlja detaljna rešenja specifičnog problema iz oblasti analitičke mehanike. Pored numeričkih postupaka u radu, izvršen je i pregled teorijskih osnova. Razne vrste analiza su vrlo česte u mašinskom inženjerstvu, zbog mogućnosti aproksimacije složenih mašina. Za predloženi sistem date su Lagranžove jednačine prve vrste, kovarijantne i kontravarijantne jednačine, Hamiltonove jednačine, generalisane koordinate, kao i uvid u Kulonovu silu trenja. Takođe, rešeni su i uslovi statičke ravnoteže uz pomoć numeričkih i grafičkih postupaka - presekom dve krive. Konačno, razmatrana je i stabilnost kretanja poremećenog i neporemećenog kretanja.In order to give an insight into the work of the machine before the production and assembly and to obtain good analysis, this paper presents detailed solutions to the specific problem occured in the field of analytical mechanics. In addition to numerical procedures in the paper, a review of the theoretical foundations was made.Various types of analysis are very common in mechanical engineering, due to the possibility of an approximation of complex machines. For the proposed system, Lagrange's equations of the first kind, covariant and contravariant equations, Hamiltons equations and the generalized coordinates, as well as insight in Coulumb friction force are provided.Also, the conditions of static equilibrium are solved numerically and using intersection of the two curves. Finally, stability of motion for the disturbed and undisturbed system was investigated

Teacher research: From theoretically-conceptual framework to the practice landmarks.

Teacher research is long– known concept in pedagogical literature and the phenomenon not new in the practice. However, there are different ways of conceptualising this kind of research and many dilemmas concerning its realization. This paper searches for the landmarks which could be useful if we want to encourage, research and realize this kind of research. Our search involves: 1. Clarification of the theoretical conceptual framework of teacher research; 2. Presentation and explanation of the general teacher research characteristics; 3. Discussion of the characteristics that the successful research of this kind have. The paper gives the analysis, integration and interpretation of different sources: literature on the contemporary tendencies in pedagogical epistemology and methodology (particularly postmodern and critically oriented), literature on teachers’ research and the experiences of teachers researching own practice. The most important landmarks are: 1. Teacher research should be based on the teacher’s research attitude and issues which are relevant for him/her; 2. Inseparability of research, practice and professional development; 3. Critical nature and change as the part of research process

Obrazovanje nastavnika za refleksivnu praksu

Educating Teachers for Reflective Practice:The understanding of the characteristics of the education for the re- flective practice and development of such an education is based on the way we understand the concepts of a teacher as the reflective practitioner and reflective practice. These concepts do not cover only the individual characteristics of a teacher and his/her practice but the aspects of the particular approach to a teacher profession too. The approach to a teacher as to a reflective practitioner encompasses teachers’ competences, his/her way of acting and the comprehensive understanding of the teaching profession as a whole, cognition and exploration of the education issues, institutions and the teacher’s position and his/her actions in relation to the institutional and wider context. The basic characteristics of this approach are:The way it responds to the epistemology issues: the unity of theory and practice, and spiral cycle of action, evaluation and reflection;The way it looks at the meaning and the purpose of the reflective practice: the development of the individual and environment, development of the theory and practice

Investigations of combustion process in combined cooker-boiler fired on solid fuels

The aim of the investigation was to make some reconstructions on the existing stove used for cooking and baking and to obtain the combined cooker-boiler which will fulfill the demands of European standard EN 12815. Implementation of modern scientific achievements in the field of combustion on stoves and furnaces fired on solid fuels was used. During the investigations four various constructions were made with different fresh air inlet and secondary air supply with the intention to obtain more complete combustion with increased efficiency and reduced CO emission. Three different fuels were used: firewood, coal, and wood briquette. A numerous parameters were measured: fuel weight changes during the combustion process, temperature of inlet and outlet water, flue gas composition (O2, CO, SO2, CO2, NOx), flue gas temperature, ash quantity etc. The result of the investigations is the stove with the efficiency of more than 75% - boiler Class 1 (according EN 12815) and CO emission of about 1% v/v. The results obtained during the measurements were used as parameters for modeling of combustion process