480 research outputs found
Tropospheric Degradation of Perfluorinated Aromatics: A Case of Hexafluorobenzene
The major tropospheric removal process for hexafluorobenzene is its oxidation by hydroxyl (OH) radicals. However, there is no information on the reaction mechanism of this important process. All geometries and energies significant for the tropospheric degradation of hexafluorobenzene were characterized using the MP2/6-311+G(d,p) and/or G3 methods. It was found out that the addition of OH radical to hexafluorobenzene proceeds via a prereaction complex. In the prereaction complex the OH radical is almost perpendicular to the aromatic ring and oxygen is pointing to its center. The reaction rate constants for addition of OH radical to hexafluorobenzene were determined for the temperature range 230ā330 K, using RRKM theory and corrected G3 energies. For the whole range of environmentally relevant temperatures (230ā330 K) there is a very good qualitative agreement between the calculated and experimental rate constants. Finally, our results almost perfectly reproduce the unusually weak temperature dependence for OH radical addition to hexafluorobenzene
Inhibition of Hill Reaction by 3-Alcoxyuracil Derivatives: QSAR Study With Topological Indices
This study was undertaken to find cl simple and accurate structural parameter for the quantitative description of inhibitory potency of alcoxyuracils in the Hill reaction and to gain more information about the mechanism of inhibition on the molecular level. A very good correlation (1\u27 = 0.987) was obtained between pho values (negative logarithm of the concentration that causes 50% inhibition) and the valence first-order and the fifth-order molecular connectivity indices. This model, when compared with the empirical models based on the n-octanol/water partition coefficients, shows superior or at least comparable performances in accuracy and range of applicability. In addition, the direct correspondence between molecular structure and the above connectivity indices make s it possible to locate structural features responsible for the inhibitory potency of alcoxyuracils in the Hill reaction and to learn more about the mechanism of inhibition on
the molecular level. From our QSAR analysis, the interaction
between the chloroplast receptor site and alcoxyuracils, which
cause inhibition of Hill reaction, can he viewed as a two-stage
mechanism. The first stage is a complex formation beteween the
uracil ring and some active site of chloroplast. The second stage
is a hydrophobic interaction between the alcoxy chain and cl hydrophobic region close to the active site. It is assumed that this stage proceeds by the Ā»zipper- mechanism and that it accounts
or the quantitative differences in inhibition found for the studied
alcoxyuracils
Problem-Based Teaching of Literature
The problem-based teaching of literature is a contemporary teaching model that has emerged from the need to overcome the weaknesses of traditional teaching and to increase the efficiency of educational work. Unlike the traditional paradigms that focused on the teacher and the lecturing model of education, the problem-based teaching of literature engages students, places them at the centre of the teaching process, and encourages them to independently define and research the problem. The problem-based teaching of literature is based on the studentsā active relationship to literary phenomena, while the teacher functions as the initiator and motivator of the studentsā versatile creations that are reached by solving problem-based tasks. This paper explores the problem-based teaching of literature and presents the results and discussion of the conducted research on the attitudes of Croatian language teachers on the problem-based teaching of literature. Fifty Croatian language teachers participated in the research by filling a survey in an attempt to determine how often the respondents use the problem-based teaching of literature as well as which forms, methods and methods of teaching they use. More specifically, the aim was to determine how teachers see their own role and studentsā activity in problem-based teaching of literature. In addition, the research sought to find out whether teachers believe that learning outcomes are more successfully achieved in the problem-based teaching of literature and what the reasons for the (un)acceptability of the problem-based teaching of literature are
Theoretical Study of Triafulvene, Fulvene, Heptafulvene, and Their 0- and N-Heteroanalogs
The geometry, electronic structure, and the aromatic stability of
triafulvene, fulvene, heptafulvene, and their 0- and N-heteroanalogs
have been investigated by t;he PPP-CI MO method. Energy
minimization with respect to bond lengths has been carried out in
order to find the optimal geometry of the studied compounds.
Aromatic stability predictions are based on the topological resqnance
energy, TRE, approach. Theoretical results are in very good agreement
with experimental measurements
The relationship between realistic and free color selection in the visual expression of preschool-aged children
ZavrÅ”ni rad Odnos realistiÄnog i slobodnog odabira boje u likovnom izrazu djece rane predÅ”kolske dobi sadrži teorijsko znanje o boji te istraživanje izvedeno putem praktiÄne aktivnosti u djeÄjem vrtiÄu āÄakovoā. Uzorak se sastojao od 20 djece, 10 radova iz mlaÄe skupine te 10 radova iz starije skupine. Kvalitativnom analizom djeÄjih radova provjerile su se postavljene hipoteze, kako bi se provjerilo koliko Äe realno djeca likovno izraziti boje na crtežu s motivom viÄenog voÄa i povrÄa te utvrditi razlike u prikazu s obzirom na dob. Rezultati ovoga istraživanja ispunili su oÄekivanja; analizirajuÄi djeÄje radova dobila sam potvrdu da su djeca u mlaÄoj dobnoj skupini od 3-4 godine sposobna prikazati stvaran i realan prikaz boja motiva na crtežu kao i starija dobna skupina od 5-6 godina.Final work the relationship between realistic and free color selection in the artistic expression of early pre-school children includes theoretical knowledge of color and research carried out through practical activities in the Äakovo pre-school The sample consisted of 20 children, 10 works from the younger group and 10 works from the older group. Qualitative analysis of child labor, hypotheses are being tested to determine how well the art-colored paint on a drawing with the motif of seen fruit and vegetables will determine the difference in age view. The results of this research have met expectations; analyzing children's work, I got the confirmation that children in the younger age group of 3-4 years are able to present a real and realistic picture of paint motifs on the drawing as well as an older age group of 5-6 years
LEGAL STATUS OF THE INSOLVENCY ADMINISTRATOR IN CASES OF SUBSEQUENTLY FOUND ASSETS OF INSOLVENT DEBTORS IN SHORTENED BANCRUPCY PROCEDURE
SteÄajni postupak se provodi radi skupnoga namirenja vjerovnika steÄajnog dužnika unovÄenjem njegove imovine i podjelom prikupljenih sredstava vjerovnicima. Ukoliko se pretpostavi zbog nedostataka podataka o imovini da steÄajni dužnik nema nikakvu imovinu ili ima imovinu manje vrijednosti koja nije dovoljna za pokrivanje troÅ”kova steÄajnog postupka trgovaÄki sudovi provode skraÄene steÄajne postupke nad steÄajnim dužnicima u kojima otvaraju i zakljuÄuju u istome danu skraÄene steÄajne postupke. Naknadno se u pojedinim sluÄajevima dolazi do saznanja da neki steÄajni dužnici nad kojima je proveden skraÄeni steÄajni postupak, a koji su veÄ po zakonu brisani iz sudskog registra posjeduju imovinu koja je dovoljna za podmirenje troÅ”kova steÄajnog postupka i djelomiÄno ili potpuno namirenje vjerovnika. SteÄajni upravitelji na koje su preÅ”la prava tijela steÄajnih dužnika, obavijeÅ”tavaju trgovaÄke sudove o postojanju imovine steÄajnih dužnika te predlaže ponovno otvaranje zakljuÄenih steÄajnih postupaka radi naknadne diobe. PraktiÄna provedba steÄajeva nad steÄajnim dužnicima u skraÄenim steÄajnim postupcima kod kojih je naknadno pronaÄena imovina Äesto nema odgovorajuÄu definiranu zakonsku podlogu steÄajnog upravitelja u steÄajnom zakonu te se steÄajni upravitelji u provedbi steÄajeva nad steÄajnim dužnicima u skraÄenim steÄajnim postupcima kod kojih je naknadno pronaÄena imovina susreÄu s brojnim problemima. SteÄajni upravitelji smatraju da sadaÅ”nji zakonski okvir koji odreÄuje pravni položaj steÄajnih upravitelja u upravljanju naknadno pronaÄenom imovinom ima nedostatke te bi se njegovom promjenom poboljÅ”ala pravna zaÅ”tita i ekonomska korist od naknadno pronaÄene imovine steÄajnih dužnika, a time i poveÄala razina namirenja vjerovnika.The bankruptcy procedure is conducted for the collective settlement of the debtor's creditors by paying his assets and allocating funds to the creditors. If it is assumed, due to the lack of data on assets, that the bankruptcy debtor does not have any assets or has less valuable assets that are insufficient to cover the costs of bankruptcy procedure, commercial courts execute shortened bankruptcy procedure on bankruptcy debtors in which they open and conclude shortened bankruptcy procedure on the same day. In some cases, it is subsequently found that some bankruptcy debtors over which the shortened bankruptcy procedures were carried out and which were already removed from the court registry have the assets that are sufficient to settle the costs of the bankruptcy procedures therefore partly or completely settling the creditor. The bankruptcy managers to whom the rights of the bankruptcy debtor are transferred, inform the commercial courts of the existence of the assets of the bankruptcy debtor and proposes the reopening of concluded bankruptcy proceedings for subsequent divisions. The practical implementation of bankruptcy procedures over debtors in shortened bankruptcy procedures with subsequently found assets often lacks the legally defined role of the insolvency administrator within the bankruptcy law which puts insolvency administrators during the implementation of bankruptcy procedures in cases of subsequently found assets in difficult position with many problems. Insolvency administrators believe that the current legal framework defining the legal position of insolvency administrators in the management of subsequently found assets has its shortcomings and that its change would improve the legal protection and economic benefits of subsequently found assets of bankruptcy debtors therefore increasing the level of settlement of creditors
Influence of health factors on school failure
UspjeÅ”nost uÄenika u usvajanju znanja i vjeÅ”tina tijekom Å”kolovanja, vrednovanu rezultatima i postignuÄem na ispitima prema unaprijed odreÄenim kriterijima, nazivamo Å”kolskim uspjehom. Å kolski neuspjeh se oÄituje kao trajan neuspjeh u svim ili nekim predmetima, ponavljanju razreda, prekidu Å”kolovanja, ali i uÄenikovom osjeÄaju neuspjeha. Cilj ovoga preglednog rada je prikaz zdravstvenih Äimbenika Å”kolskog neuspjeha. IzvrÅ”eno je pretraživanje literature u bibliografskim bazama PubMed i HrÄak, u razdoblju od 2008. do 2018. godine, koriÅ”tenjem kljuÄnih rijeÄi na hrvatskom: Å”kolska djeca, Å”kolski uspjeh, Å”kolski neuspjeh, Äimbenici Å”kolskog neuspjeha i engleskom jeziku: school performance, school attainment, school-aged children, obesity, sleep, school success, physical activity. Rezultati do sada provedenih istraživanja pokazali su povezanost nezdravih životnih navika, kao Å”to su nedovoljno sna, neredovita i nekvalitetna prehrana, sedentarni naÄin života te pretilost i pothranjenost, s loÅ”ijim Å”kolskim uspjehom. Navike zdravog stila života, kao Å”to su pravilan raspored obroka, unos zdravih namirnica, rijetka konzumacija zaslaÄenih piÄa i brze hrane te redovita tjelesna aktivnost, bili su povezani s boljim obrazovnim ishodima.
Razumijevanje povezanosti zdravstvenih Äimbenika i Å”kolskog uspjeha doprinijet Äe podizanju svijesti znanstvene i struÄne javnosti o važnosti razvoja i oÄuvanja zdravih životnih navika tijekom Å”kolovanja, kako bi se ostvarili akademski potencijali.The success of the student in acquiring knowledge and skills durings schooling, evaluated by results and achievement in exeminations according to predefined criteria, is called school success. School failure occurs as a permanent failure in all or some school subjects, grade retention, drop out of school, as well as children's feelings of failure. The aim of this paper is to show the health factors of school failure. PubMed and HrÄak databases were used for literature research in period from 2008 to 2018, using the keywords in Croatian and English: school performance, school attainment, school-aged children, obesity, sleep, school success, physical activity. The results of the research have shown the connection between unhealthy habits, such as insufficient sleep, irregular and poor quality diet, sedentary lifestyle, obesity and malnutrition, with poorer school success. Healthy habits, such as regular eating, healthy food intake, infrequent consumption of fast-food and sweetened beverage and regular physical activity, were associated with better educational outcomes. Understanding the relationship between health factors and school success will contribute to raising the awareness of the scientific and professional public on the importance of developing and preserving healthy lifestyles during schooling in order to achieve academic potentials
Structural characterization of dipeptidyl peptidase III from the bacterium Bacteroides thetaiotaomicron
Dipeptidil-peptidaza III (DPP III) je Å”iroko rasprostranjena citosolna metalopeptidaza iz porodice M49, koja odcjepljuje dipeptide s N-kraja peptidnih supstrata. VeÄina istraživanja o DPP III napravljena je na ortolozima iz eukariota koja ukazuju na njenu opÄu funkciju u intracelularnom katabolizmu proteina, ulogu u regulaciji boli te odgovoru na oksidativni stres.
U ovom radu je strukturno karakterizirana prva prokariotska DPP III, i to iz bakterije Bacteroides thetaiotaomicron, ljudskog simbionta koji nastanjuje tanko i debelo crijevo. KinetiÄkom analizom utvrÄeno je da je Arg2-2-naftilamid njezin najbolji sintetski supstrat. Elektroforetskim metodama je utvrÄeno da proÄiÅ”Äeni proteinski uzorak sadrži tri forme DPP III. Zamjenom svih cisteinskih ostataka u serinske pripremljen je dovoljno homogen uzorak za kristalizaciju bakterijske DPP III. RijeÅ”ene su strukture u otvorenoj i zatvorenoj konformaciji proteina. Pokazalo se da ovaj protein pripada istoj strukturnoj klasi kao i ljudska i kvaÅ”Äeva DPP III. S obzirom na gotovo jednako aktivno mjesto može se pretpostaviti i isti mehanizam djelovanja.Dipeptidyl peptidase III (DPP III) is a widespread cytosolic metalopeptidase of the M49 family, which cleaves dipeptides from the N-terminus of its peptide substrates. Previous studies of the DPP III enzyme were focused on eukaryotic orthologs and indicate its general function in the intracellular protein catabolism, pain regulation as well as the response to oxidative stress.
In this work, the first prokaryotic DPP III, that from the human gut symbiont bacterium Bacteroides thetaiotaomicron, was structurally characterized. Kinetic analysis showed that Arg2-2-naphthylamide is the preferred synthetic substrate. Electrophoretic methods revealed that the purified protein sample contains three forms. By replacing all cysteine residues with serines, homogeneity of the sample improved enough to enable successful crystallization of the bacterial DPP III. Structures in open and closed conformations were solved and they have the same protein fold as the human and yeast DPP III. Considering the fact that these three enzymes have almost identical active sites, the same mechanism of action can be assumed
Navigation under influence of the current, wind and seas
U ovom radu se obraÄuje problematika utjecaja vanjskih Äimbenika na brod u plovidbi, prije svega utjecaj morske struje, vjetra i valova. Na utjecaj prethodno navedenih Äimbenika na brod u plovidbi se ne može izravno utjecati, nego Äasnici na brodu moraju, uz pomoÄ podataka koji se o tim Äimbenicima dobivaju uz pomoÄ proraÄuna te raznih pomorskih izvjeÅ”taja, prilikom planiranja te izvoÄenja putovanja te Äimbenike imati na umu te u skladu s njima postupati. U svakodnevnim situacijama, svaki brod se nalazi na izravnim udarima kombinacije tih Äimbenika, a postupci u takvim situacijama su detaljno obraÄeni kroz ovaj rad.The aim of this paper is to elaborate the impact of external factors on the ship that is underway, focusing primarily on the effects of currents, winds and seas. The impact of the aforementioned factors on a ship in navigation can not be directly affected, but officers of the watch on board must, using data gathered by computing and various maritime reports, plan and carry out the voyages, bearing in mind and complying with them. In everyday situations, each ship is at all times faced with the combination of all these factors and ways of coping with them are, hereby, described in detail
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