A Structural Theorems for (m; n)-quasi-ideal Semigroups

The definition of (m; n)-ideal and (m; n)-quasi-ideal on emigroup is given in [3]. They have been studied in many papers, recently in papers [4], [5] and [6]. In this paper we introduce the notion of (m; n)-quasi-ideal semigroup and consider some general properties of this class of semigroups.Also, we introduce the notion of an (m; n)-duo quasi-ideal semigroup and give their a structural description

Structural studies on actin-ADP ribosylating binary toxin from C. difficile

Clostridium difficile infection (CDI) is a serious problem within the healthcare environment where the bacterium causes symptoms ranging from mild diarrhoea to life-threatening colitis. In addition to its principal virulent factors, Toxin A and Toxin B, some C. difficile strains produce a binary toxin (CDT) composed of two subunits namely CDTa and CDTb that are produced and secreted from the cell as two separate polypeptides. Once in the gut, these fragments have the potential to combine to form a potent cytotoxin whose role in the pathogenesis of CDI is presently unclear. This thesis is a step towards understanding structural and functional aspects of the binary toxin produced by C. difficile. The first half of this thesis (chapter I and II) provides a brief introduction to the method of structure determination of proteins molecules, i. e. X-ray crystallography and a detailed overview of C. difficile and the three known toxins from C. difficile namely – Toxin A, Toxin B and the binary toxin. Chapter II further focuses on C. difficile binary toxin and other related toxins. These toxins, known as the ADP-ribosylating toxins (ADPRTs) form a big family of potent toxins which includes Cholera, Pertussis and Diphtheria toxins and are capable of transferring the ADP-ribose part of NAD/NADPH to a varity of substrates in the target cell which ultimately results in cell death. The second half of the thesis comprises of experimental procedures that were carried out during the course of this study and their results. Cloning and expression methods for recombinant CDTa and CDTb in bacterial system followed by their purification are described with the abnormal behaviour exhibited by CDTb (chapter III). We show for the first time that purified CDTa and CDTb can combine to form an active CDT which is cytotoxic to Vero cells (Chapter IV). The purification processes described yielded milligram quantities of binary toxin fragments of high purity that led to the successful crystallisation of the proteins (chapter IV) for further functional and structural studies. High resolution crystal structures of CDTa in its native form (at pH 4.0, 8.5 and 9.0) and in complex with the ADP ribose donors -NAD and NADPH (at pH 9.0) have been determined (chapter V). The crystal structures of the native protein show ‘pronounced conformational flexibility’ confined to the active site region of the protein and ‘enhanced’ disorder at low pH while the complex structures highlight significant differences in ‘ligand specificity’ compared with the enzymatic subunit of a close homologue, Clostridium perfringens Iota toxin (Ia). These structural data provide the first detailed information on protein-donor substrate complex stabilisation in CDTa which may have implications in understanding CDT recognition. Crystallisation of CDTb yielded preliminary crystals. The optimisation of these crystallisation conditions is underway. The thesis concludes with some thoughts and discussion on future directions of this research.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

IDENTIFIKACIJA KRITERIJUMA KVALITETA OTVORENIH PROSTORA U STAMBENIM NASELJIMA SA VIŠEPORODIČNIM STANOVANJEM U PROCESU URBANE REVITALIZACIJE

The correlation between the quality of open spaces and quality of life in high-rise housing neighborhoods in contemporary urban-architectural and social frameworks has been confirmed by a series of multidisciplinary researches. Modern research indicates that in the process of revitalization, it is necessary to look at various aspects of the quality of open spaces in order to provide a more efficient degree of improvement. Creating adequate spatial conditions for the different types of activities of the daily spare time of tenants and the exercise of physical activity in the direction of improving psycho-physical health, achieving spatial-ambient values, as well as for encouraging good neighborly relations, communion, territoriality and sense of belonging, which are all determinants of the quality of life, can be managed by providing a certain level of quality open spaces. Bearing in mind that there are no unique criteria for the quality of open spaces in high - rise residential neighborhoods, the aim of this paper is to indicate the desirable characteristics of these spaces in accordance with the contemporary principles of urban design and practice in the process of their revitalization. Therefore, residential neighborhood Poptahof has been selected as a research platform that represents the good practice example of the revitalization of open spaces in line with identified criteria and quality aspects. These criteria can serve as a basis for further research of the modes of urban revitalization of open spaces, with the aim of improving the quality of life.Korelacija između kvaliteta slobodnih prostora i kvaliteta života u stambenim naseljima sa višeporodičnim stanovanjem u savremenim urbanističko-arhitektonskim i socijalnim okvirima potvrđena je nizom multidisciplinarnih istraživanja. Savremena istraživanja ukazuju da je u procesu revitalizacije potrebno sagledati različite aspekte kvaliteta otvorenih prostora kako bi ostvario što efikasniji stepen unapređenja. Stvaranje odgovarajućih prostornih uslova za različite vrste aktivnosti dnevnog slobodnog vremena stanara i vršenje fizičke aktivnosti u pravcu unapređenja psiho-fizičkog zdravlja, postizanja prostorno-ambijentalnih vrijednosti, kao i za podsticanje dobrosusjedskih odnosa, zajedništva, teritorijalnosti i osećaj pripadnosti, koji su sve determinante kvaliteta života, mogu se postići obezbeđivanjem određenog nivoa kvalitetnih otvorenih prostora. Imajući u vidu da ne postoje jedinstveni kriterijumi kvaliteta otvorenih prostora u stambenim naseljima sa višeporodičnim stanovanjem, cilj ovog rada je da ukaže na poželjne karakteristike ovih prostora u skladu sa savremenim principima urbanog dizajna i prakse u procesu njihove revitalizacije. Stoga je Poptahof stambeno naselje odabrano kao istraživačka platforma koja predstavlja primer dobre prakse unapređenja otvorenih prostora u skladu s utvrđenim kriterijima i aspektima kvaliteta. Ovi kriterijumi mogu poslužiti kao osnova za dalja istraživanja modaliteta urbane revitalizacije otvorenih prostora, sa ciljem poboljšanja kvaliteta života stanara stambenih naselja sa višeporodičnim stanovanjem

PRIMENA KISINDŽEROVE METODE ZA ODREĐIVANJE KINETIČKIH PARAMETARA PIROLIZE TREŠNJINOG DRVETA

In the global quest for substitution of fossil fuels, biomass is regarded as one of the most promising alternatives. Thermochemical conversion is one of the dominant biomass-to-energy processing routes with pyrolysis as one of the options that gained importance in recent years. In this paper pyrolysis experiments of cheery tree samples were performed. The objective of this research was to determine selected physical and chemical properties of cheery related to thermochemical conversion. The samples were pyrolysed in a thermogravimetric analyzer in an inert, nitrogen, atmosphere at four different heating rates 1, 2, 5 and 10 °C/min. Pyrolysis occurred, as expected, in three step: loss of moisture and light volatiles, active and passive pyrolysis. With an increase in heating rate a lateral shift of the maximum rate of weight loss for the thermal decomposition to higher temperatures was observed, as well as an increase in the amount of residual char. Moreover, kinetic studies were performed using the Kissinger method. The activation energy was calculated to be 155.26 kJ/mol, while the pre-exponential factor was 1.685×1012 min-1. Obtained results are comparable to values reported in literature. Kissinger method is straightforward and offers the possibility for fast and reliable determination of kinetic parameters.U globalnoj protrazi za zamenom fosilnih goriva, biomasa se smatra jednom od značajnih alternative. Termohemijska konverzija predstavlja jedan od dominantnih načina za iskorišćenje biomase u energetske svrhe dok je piroliza jedna od opcija koja dobija na značaju poslednjih godina. U ovom radu proučavan je proces priolize drveta trešnje u cilju određivanja fizičkih i hemijskih karakteristika, koje se odnose na termohemijsku konverziju, drveta trešnje. Najpre je izvršena piroliza uzoraka u termogravimetrijskom analizatoru, u inertnoj atmosferi azota, na četiri različite brzine grejanja 1, 2, 5 and 10 °C/min. Piroliza se odvijala, kako se i očekivalo, u tri koraka: gubitak vlage i lako isparljivih volatila, aktivna i pasivna piroiza. Porast brzine grejanja uzrokovao je lateralni pomak ka višim temperaturama svakog koraka termalne degradacije, kao i porast u količini rezidualnog koksnog ostatka. Pored toga, određeni su i kinetički parametri primenom Kisindžerove metode. Izračunato je da aktivaciona energija iznosi 155,26 kJ/mol, a pre-eksponencijalni faktor 1,685×1012 min-1. Dobijeni kinetički parametri su uporedivi sa rezultatima iz literature. Kisindžerova metoda je jednostavna i pruža mogućnost brzog i pouzdanog određivanja kinetičkih parametara