ODREĐIVANJE LOKACIJE I INTENZITETA TURBULENCIJE BURE

Učinjen je pokušaj određivanja lokacije i intenziteta turbulencije bure iz polja empiričkog indeksa za situaciju 07.03.1982. godine iz podataka ALPEX-SOP nad zapadnim područjem Jugoslavije. Osnovna je pretpostavka od koje se polazi da je turbulencija pri buri generirana Kelvin-Helmholtzovom nestabilnošću i da je stoga ovu vrslu turbulencije moguće locirati i prognozirati pomoću indikatora i prediktora turbulencije vedroga zraka. Također se predpostavlja da je intenzitet ove vrste turbulencije moguće odrediti na osnovi indikatora intenziteta CAT-a. Jedan od takvih indikatora je empirički indeks E kojega je izveo Dutton (1980) multiplom linearnom regresionom analizom. Rezultati pokazuju slaganje sa avionski izmjerenom turbulencijom bure kako je prezentirao Smith (1987)

DIJAGNOSTIČKA TENDENCIJA RICHARDSONOVOG BROJA KAO INDIKATOR TURBULENCIJE U VEDROM ZRAKU

Na temelju teorije stabiliteta stabilno stratificaranih fluida sa smicanjem primijenjene na mehanizam generiranja CAT-a, izveden ie indikator (prediktor) CAT-a u literaturi poznat pod nazivom Dijagnostička Tendencija Richardsonovog broja. Sposobnost ovog teorijskog prediktora da dijagnosticira (prognozira) CAT testirana je na slučaju kada su CAT opservirali piloti u području iznad Jugoslavije. Rezultati su dobiveni iz mjerenih podataka vjetra i temperature. Ulazna polja su dobivena metodom interpolacije u mreži točaka s horizontalnom udaljenosti od 100 km i vertikalnom rezolucijom od 100 hPa. Kritične vrijednosti za CAT su određene uspoređivaniem s područjima u kojima su neki drugi prediktori dijagnosticirali CAT i područjima u kojima su CAT opservirali piloti

The relationship between epistemic and motivational beliefs and student engagement in chemistry

Cilj ovog istraživanja bio je ispitati povezanost epistemičkih i motivacijskih uvjerenja s uključenosti učenika u nastavu I učenje kemije. Kao teorijski okvir korištena je Teorija očekivanja i vrijednosti koju su razvili Wigfield i Eccles (2000). U istraživanju je sudjelovalo 346 učenika drugih i trećih razreda opće gimnazije. Učenici su ispunjavali skale uključenosti, epistemičkih uvjerenja (evaluacija i nedvojbenost), samoefikasnosti, samoefikasnosti za samoregulaciju učenja i subjektivne vrijednosti pridane kemiji. Subjektivna vrijednost i samoefikasnost za samoregulaciju učenja pokazali su se kao značajni prediktori kognitivne i bihevioralne uključenosti: što su veće procjene na tim skalama,veće su i procjene bihevioralne i kognitivne uključenosti. Viša evaluacija, subjektivna vrijednost i samoefikasnost za samoregulaciju učenja predviđaju veću ugodnu emocionalnu uključenost. Samoefikasnost i nedvojbenost značajno predviđaju neugodnu emocionalnu uključenost: više vrijednosti na tim skalama predviđaju veću neugodnu emocionalnu uključenost. Prediktorske varijable objasnile su značajan dio varijance svih dimenzija uključenosti u nastavu i učenje kemije, a najviše su doprinijele objašnjavanju ugodne emocionalne uključenosti. Neugodna emocionalna uključenost najmanje je objašnjena uključenim prediktorskim varijablama.The aim of this study was to examine the relationship between epistemic and motivational beliefs and student engagement in chemisty. Expectancy-value model developed by Wigfield and Eccles (2000) was used as a theoretical framework. Participants were 346 second-year and third-year high school students. Instruments assessing student engagement, epistemic beliefs (certainty and justification), students' self-efficacy beliefs, self-regulatory efficacy, and subjective task values were used in this study. Subjective task value and self-regulatory efficacy were identified as significant predictors of cognitive engagement and behavioral engagement: higher values on those scale predict higher values on cognitive engagement and behavioral engagement scale . Justification, subjective task value and self-regulatory efficacy emerged as significant predictors of positive emotional engagement: the higher values on those scales, the higher estimated positive emotional engagement. Higher values on self – efficacy beliefs and certainty scale predicted higher negative emotional engagement. The results have shown a significant contribution of epistemic and motivational beliefs in prediction of student engagement in chemistry. Predictor variables have shown greatest cotnribution in explaining positive emotional engagement, and smallest contribution in predicting negative emotional engagement

Supplementary data for article: Šovrc, Ľ.; Borovska, K.; Cinková, K.; Stanković, D.; Planková, A. Advanced Electrochemical Platform for Determination of Cytostatic Drug Flutamide in Various Matrices Using a Boron-Doped Diamond Electrode. Electrochimica Acta 2017, 251, 621–630. https://doi.org/10.1016/j.electacta.2017.08.077

Supplementary material for: [https://doi.org/10.1016/j.electacta.2017.08.077]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2540]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/2996

Chemical Composition and Protective Possibilities of Juglans Nigra Leaves and Green Husks Extracts: DNA Binding and Micronucleus Assay in Human Lymphocytes

To better understand the mechanism of action of the compounds in the ethanolic extracts of J. nigra leaves and green husks, their binding to CT-DNA was investigated. This study was conducted to elucidate the in vitro protective effect of extracts against chromosomal damage in mitogen-induced human lymphocytes and investigate the possible application of selec+ted extracts as a natural source of polyphenolic compounds. Using HPLC-MS analysis, 103 different compounds were identified as having a higher number of active species, which is consistent with their activity. The frequency of micronuclei (MN) was scored in binucleated cells, and the nuclear proliferation index was calculated. Cyclic voltammetry experiments demonstrate that the nature of the interaction between extracts and CT-DNA is a synergy of electrostatic and intercalative modes, where leaves extracts showed a higher ability to bind to DNA. Extracts showed excellent antioxidant activity. At a concentration of only 4 μg/mL, extract of J. nigra leaves and the green husks reduced the incidence of MN by 58.2% and 64.5%, respectively, compared to control cell cultures

PartiaI Syntheses of 21,27 -Bisnordemissidine from Epiandrosterone and Dehydroepiandrosterone Acetates. Crystal and Molecular Structure of 21,27 -Bisnordemissidine Hydrobromide

Stereoselective syntheses of 21,27-bisnordemissidine from epiandrosterone acetate (1) and dehydroepiandrosterone acetate (la) are described in this work. These syntheses involve in sequence: a) stereospecific addition of «-picolyl-Iithium to the C-17 carbonyl group of 1 (la); b) regio- and chemoselective 17,20-dehydration of the formed diol 2 (2a) leading to 3~-acetoxy-17-picolinylidene- -5a-androstane (3) or the corresponding derivative 3a; c) regiospecific allylic oxidation of C-16 in 3 (3a) by Se02 to 4 and chromic acid oxidation to the crucial intermediates (5a-5d); d) stereospecific intramolecular reductive cyclization reaction of 5a-5d, under carefully chosen reaction conditions, leading to 3~-acetoxy- -21,27-bisnor-5a-solanidane (6); e) hydrolysis of 6 with conc. aq. HBr to the target molecule of 21,27-bisnordemissidine hydrobromide (7); and f) alkaline treatment of 6 and 7 with KOH in MeOH affording 21,27-bisnordemissidine (11). The structure of 7 has been unambiguously proved by the appropriate X-ray structural analysis. Detection and isolation of some intermediates and by-products (8, 9 and 10) during catalytic hydrogenation of 5c and 5d pointed to a possible mechanism of the last and crucial step of the synthesis of 21,27-bisnordemissidine

A New Approach in the Construction of Protection in Brachytherapy – Brachytherapy Chamber

Brahiterapijski uređaji sa izvorima velike aktivnosti (> 370 GBq) postavljaju se u posebne zaštitne bunkere, debljine zaštitnog betonskog zida oko 70 cm, što zahteva opsežnije građevinsko-tehničke radove i povećava cenu izrade (preko 100.000 Eura). Da bi se prevazišao problem ograničenog prostora unutar odeljenja brahiterapije, predlažemo izradu „brahiterapijske komore“ koja bi bila smeštena u aplikacionoj sali minimalne površine 30 m2. Komandni pult brahiterapijskog uređaja bi se nalazilo u parapetom/paravanom odvojenom delu sale. Brahiterapijska komora, pojedinačnih dimenzija (V x Š) oko 2 m, u obliku ćiričnog slova P (П), izrađuje se od olovnih ploča debljine 5 cm. Sa jedne strane komore (ulaz za pacijenta) navlačiće se pokretni/motorizovani paravan (debljine zida: 5 cm; dimenzija V x Š oko 2,3 m). U toku zračenja pacijent i uređaj se nalaze u komori. Cena izrade ove brahiterapijske komore sa pripadajućim elementima ne bi prelazila cenu izrade klasičnog brahiterapijskog bunkera.Brachytherapy units with high activity sources (> 370 GBq) are placed in special protective treatment rooms, with concrete wall thickness of about 70 cm, which requires more extensive construction and technical works that increases the cost of production (over 100.000 Euros). In order to overcome the problem of limited space within the brachytherapy department, we propose construction of a "brachytherapy chamber" that would be located in the application teatre with a minimum area of 30 sqm. The control unit would be located in a separated part of the treatment room. The brachytherapy chamber, with an individual dimensions (H x W) of about 2 m, in the shape of the Cyrillic letter P (П), is made of lead plates 5 cm thick. On one side of the chamber (patient entrance) a movable/motorized screen (wall thickness: 5 cm; dimensions HxW each approx. 2.3 m) will be constructed. During radiation, the patient and theunit are in the chamber. The construction cost of this brachytherapy chamber with associated elements would not exceed the cost of making a classic brachytherapy treatment room.XXXII Simpozijum Društva za zaštitu od zračenja Srbije i Crne Gore, 4-6. oktobar 2023; Budva, Crna GoraProceedings: [https://vinar.vin.bg.ac.rs/handle/123456789/11602

PartiaI Syntheses of 21,27 -Bisnordemissidine from Epiandrosterone and Dehydroepiandrosterone Acetates. Crystal and Molecular Structure of 21,27 -Bisnordemissidine Hydrobromide

Stereoselective syntheses of 21,27-bisnordemissidine from epiandrosterone acetate (1) and dehydroepiandrosterone acetate (la) are described in this work. These syntheses involve in sequence: a) stereospecific addition of «-picolyl-Iithium to the C-17 carbonyl group of 1 (la); b) regio- and chemoselective 17,20-dehydration of the formed diol 2 (2a) leading to 3~-acetoxy-17-picolinylidene- -5a-androstane (3) or the corresponding derivative 3a; c) regiospecific allylic oxidation of C-16 in 3 (3a) by Se02 to 4 and chromic acid oxidation to the crucial intermediates (5a-5d); d) stereospecific intramolecular reductive cyclization reaction of 5a-5d, under carefully chosen reaction conditions, leading to 3~-acetoxy- -21,27-bisnor-5a-solanidane (6); e) hydrolysis of 6 with conc. aq. HBr to the target molecule of 21,27-bisnordemissidine hydrobromide (7); and f) alkaline treatment of 6 and 7 with KOH in MeOH affording 21,27-bisnordemissidine (11). The structure of 7 has been unambiguously proved by the appropriate X-ray structural analysis. Detection and isolation of some intermediates and by-products (8, 9 and 10) during catalytic hydrogenation of 5c and 5d pointed to a possible mechanism of the last and crucial step of the synthesis of 21,27-bisnordemissidine

Adsorpcione karakteristike hidrogelova hitozana za uklanjanje boje kongo crveno iz vodenih rastvora

The present study investigated potential application of biopolymer chitosan, in the form of gel beads, for the removal of Congo red (CR) dye from aqueous solution. Chitosan hydrogel beads (CHBs) were prepared by a coupled ionic and covalent co-cross-linking, employing citric acid (CA) and glutaraldehyde (Glu) as an ionic and a chemical crosslinker, respectively. Batch experiments were carried out to optimize the process conditions for efficient removal of CR dye and to determine the adsorption capacity of prepared CHBs. The results showed that the highest removal efficiency of CR was obtained in the pH range from 6 to 10, and that the equilibrium was attained after 180 min. The Langmuir isotherm model provided the best correlation for the adsorption of CR onto CA/Glu cocross-linked CHBs, with the maximum adsorption capacity (qm) of 544.2 mg g-1 .Istraživanja u okviru ove studije okrenuta su ka ispitivanju mogućnosti primene hidrogelova hitozana, u obliku sfera, za uklanjanje boje kongo crveno (CR) iz vodenih rastvora. Sfere hidrogela hitozana (CHBs) pripremljene su spregnutim jonskim i kovalentnim umrežavanjem, pri čemu su limunska kiselina (CA) i glutaraldehid (Glu) korišćeni kao jonski i kovalentni umreživač, respektivno. Eksperimenti su rađeni u šaržnom sistemu kako bi se optimizovali uslovi za efikasno uklanjanje CR iz vode i odredili adsorpcioni kapaciteti sintetisanih CHBs. Eksperimentalni rezultati su pokazali da je efikasnost uklanjanja CR najveća u pH intervalu od 6 do 10, a da se ravnoteža uspostavlja nakon 180 minuta. Langmirova izoterma pokazala je najbolju korelaciju za adsorpciju CR boje na CA/Glu umreženim sferama hidrogelova hitozana, pri čemu maksimalni adsorpcioni kapacitet (qm) iznosi 544.2 mg g-1 .59th Meeting of the Serbian Chemical Society; June 1-2, 2023, Novi Sad, Serbi