<p>Adhezija i formiranje biofilma kvasaca na kontaktne povr&scaron;ine materijala je ozbiljan higijenski problem u prehrambenoj industriji, jer može biti izvor kontaminacije tokom proizvodnje, dovodeći do velikih ekonomskih gubitaka zbog kvarenja hrane i smanjenja kvaliteta proizvoda, a takođe može da &scaron;teti zdravlju potro&scaron;ača. S drge strane, mnoge infekcije u bolnici uzrokovane su adhezijom vrsta roda Candida na medicinska sredstva i implantate. Međutim, trenutno razumevanje adhezije i kolonizacije kvasaca na abiotičke povr&scaron;ine je ograničeno na samo neke vrste roda Candida, a naročito malo se zna o vrstama roda Pichia kao adhezivnim agensima.<br />Cilj istraživanja u okviru ove doktorske disertacije je bio da se proceni potencijal adhezije sojeva kvasaca Candida i Pichia na polistiren povr&scaron;inu, diskove od nerđajućeg čelika (AISI 304, Ra = 25.20 &ndash; 961.9 nm) i drveta sa različitim stepenom hrapavosti povr&scaron;ine, i ispita uticaj hrapavosti povr&scaron;ine na adheziju kvasaca. Hidrofobnost povr&scaron;ine ćelije (CSH) sojeva iz rodova Candida i Pichia je određena u cilju procene korelacije između hidrofobnosti povr&scaron;ine ćelije i adhezije kvasaca na polistiren. Pored toga, ispitan je uticaj različitih medijuma, temperatura, i različitih biljnih ekstrakata na adheziju odabranih sojeva iz rodova Candida i Pichia na povr&scaron;ine diskova od nerđajućeg čelika. Rezultati su pokazali da su svi testirani sojevi kvasaca Candida i Pichia su bili u stanju da adheriraju na polistiren, povr&scaron;ine od nerđajućeg čelika i drveta, ali u različitoj meri. Soj vrste C. albicans je imao veću sposobnost adhezije na polistiren i nerđajući čelik u odnosu na sojeve vrsta C. glabrata, C. parapsilosis i C. krusei. U slučaju kod roda Pichia, sojevi vrste P. membranifaciens su pokazali manju sposobnost adhezije na nerđajući čelik nego ispitivani soj vrste P. pijperi, &scaron;to nije slučaj kod adhezije na polistiren. Na osnovu dobijenih rezultata pokazano je da su sojevi vrsta C. glabrata, C. parapsilosis, C. krusei, P. pijperi i P. membranifaciens bili izrazito do umereno hidrofobni, dok je soj vrste C. albicans bio hidrofilan, &scaron;to ukazuje da hidrofobnost povr&scaron;ine ćelije (CSH) nije značajno u korelaciji sa količinom ćelija adheriranih na polistiren. Pored toga, na adheziju sojeva kvasaca Candida i Pichia značajno je uticala hrapavost povr&scaron;ine nerđajućeg čelika, dok hrapavost drvenih povr&scaron;ina nije značajno uticala. Dalje mi smo ispitali uticaj različitih medijuma za rast i temperature na adheziju odabranih kvasaca. Primećeno je da je količina adheriranih ćelija kvasaca C. albicans i C. glabrata na povr&scaron;inama od nerđajućeg čelika bila znatno veća u Malt Extract Broth (MEB) medijumu, dok je za C. parapsilosis, C. krusei, P. pijperi i P. membranifaciens bila u Yeast Peptone Dextrose (YPD) medijumu. Na&scaron;i podaci takođe ukazuju da je temperatura veoma važan faktor koji značajno utiče na adheziju ovih kvasaca. Problem adhezije i formiranje biofilma kvasaca na abiotičkim povr&scaron;inama i rastuća otpornost na postojeće antimikrobne agense predstavilo je izazov za nas za pronalaženjem novih alternativnih agenasa biljnog porekla. Stoga mi smo ispitali antimikrobnu i antibiofilm aktivnost biljnih ekstrakata kao &scaron;to su Humulus lupulus, Alpinia katsumadai i Evodia rutaecarpa prema C. albicans, C. glabrata i P. membranifaciens. Na osnovu dobijenih MIC vrednosti, testirani biljni ekstrakati su bili efikasni u inhibiciji kvasaca. Primećeno je da su biofilmovi C. glabrata pokazali veću otpornost na biljne ekstrakte u odnosu na C. albicans. Međutim, ekstrakti A. katsumadai i E. rutaecarpa su promovisani rast i razvoj formiranog biofilma P. membranifaciens.</p> / <p>The adhesion and biofilm formation of yeast on the contact surfaces of the material is a serious hygiene problem in the food industry, because it can be a source of contamination during production, leading to major economic losses due to food spoilage and reduced product quality, and can also affects the consumer&rsquo;s health. On the other hand, many infections in the hospital are caused by the adhesion of Candida spp. to medical devices and implants. However, the understanding of adhesion and colonization of yeasts on abiotic surfaces is limited to only some Candida species, and in particular little is known about Pichia species as adhesive agents.<br />The aim of the research in this doctoral dissertation was to assess the potential of Candida and Pichia strains to adhere to polystyrene surface, stainless steel discs (AISI 304, Ra = 25.20 - 961.9 nm) and wood (beech) with different degrees of surface roughness, and examined the influence of surface roughness on yeast adhesion. Cell surface hydrophobicity (CSH) of Candida and Pichia strains was determined in order to assess the correlation between the cell surface hydrophobicity and the yeast adhesion to polystyrene. In addition, the influence of different medium, temperature, and various plant extracts on the adhesion of selected Candida and Pichia strains to to stainless steel surfaces was examined. Our results indicated that all Candida and Pichia strains were able to adhere to polystyrene, stainless steel surfaces and wood in a species- and strain-dependent manner. C. albicans had a higher ability to adhere to polystyrene and stainless steel compared to C. glabrata, C. parapsilosis and C. krusei. Regarding Pichia species, P. membranifaciens strains were less adherent to stainless steel than P. pijperi, what is not the case in the adhesion to polystyrene. Based on the results obtained, C. glabrata, C. parapsilosis, C. krusei, P. pijperi i P. membranifaciens strains were strongly to moderately hydrophobic while only C. albicans was moderately hydrophilic, indicating that the cell surface hydrophobicity is not significantly correlated with the amount of cells adhered to polystyrene. In addition, the adhesion of Candida and Pichia strains was significantly influenced by the roughness of stainless steel surface, while the roughness of wood surfaces did not significantly influence. Further on we examined the impact of different growth medium and temperature on adhesion of selected yeasts. It was noted that the amount of adhered cells of C. albicans and C. glabrata on stainless steel surfaces were significantly higher in the Malt Extract Broth (MEB) medium, whereas for C. parapsilosis, C. krusei, P. pijperi and P. membranifaciens it was Yeast Peptone Dextrose (YPD) medium. Our data also indicated that temperature is a very important factor which considerably affects the adhesion of these yeast. The problem of yeast adhesion and biofilm formation on abiotic surfaces and its growing resistance to existing antimicrobial agents, presented a challenge for us to find new alternative agents of plant origin. Hence, we investigated antimicrobial and antibiofilm activity of plant extracts such as Humulus lupulus, Alpinia katsumadai and Evodia rutaecarpa against C. albicans, C. glabrata and P. membranifaciens. According to the MIC values, all plant extracts were effective in the inhibition of yeast strains. It was observed that biofilms of C. glabrata are more resistance to plant extracts as compared to C. albicans. However, extracts of A. katsumadai and E. rutaecarpa were promoted the growth and development of a preformed biofilm of P. membranifaciens.</p>

<p>&Scaron;iroka upotreba imunosupresivnih terapija zajedno sa antimikotičnim terapijama &scaron;itokog spektra značajno je povećala učestalost povr&scaron;inskih i sistemskih infekcija uzrokovanih patogenim kvascem Candida glabrata. Zbog povećane rezistentnosti vrste C. glabrata na klasične antimikotike, javila se potreba za pronalaskom novih alternativa u prevenciji i lečenju infekcija izazvanih ovim patogenom. Tokom poslednjih nekoliko godina se u velikoj meri razmatra potencijalni benefit probiotskih mikroorganizama na zdravlje ljudi. Pored primene brojnih probiotskih bakterija, Saccharomyces boulardii je jedina vrsta kvasca za koju je dokazano da poseduje svojstva koja karakteri&scaron;u probiotike.<br />Cilj istraživanja ove doktorske disertacije je ispitivanje uticaja probiotskog kvasca S. boulardii na adheziju kvasca C. glabrata na polistitren povr&scaron;inu pri različitim temperaturama, pH vrednostima i u prisustvu različitih koncentracija tri klinički važna antimikotika kao &scaron;to su flukonazol, itrakonazol i amfotericin B. Hidrofobnost povr&scaron;ine ćelije (CSH) sojeva kvasca C. glabrata je određena u cilju procene korelacije između ove fizičko-hemijske osobine i adhezije na polistiren povr&scaron;inu. Pored toga, ispitana je adhezija kvasca C. glabrata u ko-kulturi sa drugim vrstama mikroorganizama. Testirana su tri soja kvasca C. glabrata, kvasci Candida krusei i Saccharomyces cerevisiae, kao i dve vrste probiotskih bakterija Lactobacillus rhamnosus i Lactobacillus casei. Metoda kori&scaron;ćena za procenu adhezije bila je bojenje kristal violetom, dok je hidrofobnost povr&scaron;ine ćelije sojeva kvasca C. glabrata određena testom Mikrobne adhezije na ugljovodonike.<br />Na&scaron;i rezultati su pokazali da uprkos neadhezivnosti ćelija probiotskog kvasca S. boulardii, ovaj probiotik je značajno uticao na sposobnost adhezije kvasca C. glabrata. Ovaj efekat je bio veoma zavisan od sojeva vrste C. glabrata, i bio je antagonistički ili sinergistički. &Scaron;to se tiče faktora životne sredine, temperatura nije pokazala značajan uticaj na modulatorni efekat probiotskog kvasca S. boulardii, dok pri visokoj pH vrednosti, probiotski kvasac nije uspeo da potisne adheziju sojeva kvasca C. glabrata. Sličan efekat je primećen u eksperimentima sa antimikoticima, gde su povećane koncentracije antimikotika smanjile modulatorni efekat S. boulardii na adheziju C. glabrata. Sojevi vrste C. glabrata u ko-kulturi sa neadhezivnim patogenim sojevima vrsta C. krusei i S. cerevisiae su pokazali slabiju adheziju nego u ko-kulturi sa neadhezivnim probiotskim sojevima vrste S. boulardii, L. rhamnosus i L. casei. &Scaron;to ukazuje da se adhezivnost dve odvojene kulture ne može korisiti za predviđanje adhezivnosti njihove ko-kulture. Nije utvrđena korelacija između hidrofobnosti povr&scaron;ine ćelije i adhezije na polistiren povr&scaron;inu sojeva kvasca C. glabrata, &scaron;to ukazuje da hidrofobnost ćelijskog zida ne mora uvek da bude precizna mera adhezivnog potencijala.</p> / <p>Following the widespread use of immunosuppressive therapy together with broadspectrum antimycotic therapy, the frequency of mucosal and systemic infections caused by the pathogenic yeast Candida glabrata has increased in the past decades. Due to the resistance of C. glabrata to existing azole drugs, it is very important to look for new strategies helping the treatment of such fungal diseases. An increasing number of potential health benefits are being attributed to probiotic treatments. They include various bacterial probiotics, while among yeast only Saccharomyces boulardii (nom. nud.) is used extensively as a probiotic and often marketed as a dietary supplement.<br />The aim of this doctoral dissertation is to investigate the effect of the probiotic yeast S. boulardii on the adhesion of C. glabrata to polystyrene surface at different temperatures, pH values, and in the presence of three clinically important antifungal drugs, namely fluconazole, itraconazole, and amphotericin B. The cell surface hydrophobicity (CSH) of the tested C. glabrata strains has been determined as well in order to test for a possible correlation between this physico-chemical property and the ability to adhere to polystyrene surface. In addition, Candida krusei, Saccharomyces cerevisiae, two bacterial probiotics Lactobacillus rhamnosus and Lactobacillus casei were tested in a co-culture with C. glabrata as well. The method used to assess adhesion was crystal violet staining. The CSH of C. glabrata strains was determined using the Microbial Adhesion To Hydrocarbon (MATH) test. Our results showed that despite the nonadhesiveness of S. boulardii cells, this probiotic significantly affected the adherence ability of C. glabrata. This effect was highly dependent on C. glabrata strain and was either antagonistic or synergistic. Regarding the extrinsic factors, temperature did not indicate any significant influence on this S. boulardii modulatory effect, while at high pH, S. boulardii did not manage to repress the adhesion of C. glabrata strains. Similar effect was observed in the experiments with antimycotics, where increased concentrations of antimycotic reduced the modulatory effect of S. boulardii on C. glabrata adhesion. C. glabrata strains in the co-cultures with non-adhesive pathogenic strains C. krusei and S. cerevisiae showed weaker adhesion than in co-cultures with non-adhesive probiotic strains S. boulardii, L. rhamnosus and L. casei. This indicates that the adhesiveness of two separate cultures could not be used to predict the adhesiveness of their co-culture. Further, there is no correlation between cell surface hydrophobicity and adhesion of C. glabrata strains to the polystyrene surface, which indicates that the hydrophobicity of the cell wall must not always be the precise measure of the adhesive potential.</p>

Baigiamajame magistro darbe nagrinėjamos elektrolankiniu purškimu skirtingomis vielomis užpurkštos dangos. Atlikta terminio purškimo dangų, jų technologijų apžvalga ir analizė, pateikta dangų tyrimo metodika. Metalo paviršinis sluoksnis dengiamas siekiant pakeisti jo mechanines bei fizikines savybes, suteikti atsparumą išorės poveikiui ir pagerinti estetinį vaizdą. Atlikti nerūdijančio plieno, jūrinės bronzos bei jų kombinuotos dangų mikrostruktūros, mikrokietumo, dangos tamprumo modulio bei adhezijos tyrimai. Gauti rezultatai pateikti grafiškai. Išnagrinėjus praktinius ir skaitinius terminio purškimo dangų rezultatus, pateikiamos baigiamojo darbo išvados. Darbą sudaro 5 dalys: įvadas, literatūros šaltinių apžvalga ir analizė, elektrolankiniu purškimu gautų dangų tyrimai, išvados, literatūros sąrašas. Darbo apimtis – 59 p. teksto, 55 iliustr., 14 lent., 18 bibliografinių šaltinių. / In the final master thesis examined coatings by arc spraying with different solid wires. The review of thermal spray coatings technology and research methods are described. The metal surface coating was applied to modify it‘s mechanical and physical properties, also resistance to external impact and improve aesthetics view. The research of stainless steel, marine bronze and combined coating microstructures, microhardness modulus of elesticity and adhesion were carried out. The results are presented graphically. The experimental and numerical results of thermal spray coatings were analysed and conclusions were given. Structure of work: introduction, literature review and analysis, research of coatings by arc spraying, coclusions, references. Thesis consist of – 59 p. text, 55 pictures, 14 tables, 18 bibliografical entries.

The goal of the dissertation was to investigate the peculiarity of morphological changes of the modified polychloroprene adhesive in the aim to predict the mechanical and adhesive behaviour and to produce composition with useful and essential properties.

<p>Razvijene su TiAlN/TiSiN i CrAlN/TiSiN nanoslojne prevlake u kojima je napravljen spoj nanoslojnog i nanokompozitnog dizajna. Akcenat je stavljen na proizvodnju prevlaka visoke tvrdoće i visoke otpornosti na lom. Proučavane su i jednoslojne TiAlN, nanokompozitne TiSiN i višeslojne TiAlN/TiSiN prevlake kako bi se utvrdilo kako dizajn utiče na osobine prevlaka. Sve prevlake pripremane su sa jednim, dva i tri stepena rotacije. Pokazano je da dizajn i vid rotacije značajno utiču na mikrostrukturu i teksturu prevlaka, a time na njihove mehaničke osobine, otpornost na lom, adheziju između prevlake i podloge, topografiju površine i tribološko ponašanje. Nanoslojne i nanokompozitne prevlake odlikuju se kompaktnom nanokristalnom mikrostrukturom, dok jednoslojne TiAlN prevlake imaju stubastu strukturu sa kristalnim zrnima veće veličine. Pri prelasku sa jednog na više stepeni rotacije mikrostruktura prevlaka postaje kompaktnija sa kristalnim zrnima manje veličine i manjom poroznošću. U skladu sa tim, najmanju hrapavost, najveću tvrdoću, najveću otpornost na lom i najveću otpornost na habanje imaju nanoslojne i nanokompozitne prevlake pripremane sa dva i tri stepena rotacije.</p> / <p>With the aim to develop hard coatings characterized by both, high hardness<br />and high resistance to cracking, synergy between nanolayered and<br />nanocomposite design was made and nanolayered TiAlN/TiSiN and<br />CrAlN/TiSiN coatings were produced. Monolayer TiAlN, nanocomposite<br />TiSiN and multilayer TiAlN/TiSiN were also studied in order to find the<br />relation between the coating design and their properties. All coatings were<br />deposited with 1-fold, 2-fold and 3-fold rotation. It is shown that coating<br />design and type of rotation have great influence on coating microstructure<br />and texture, and in this way on their mechanical properties, resistance to<br />cracking, adhesion between coating and substrate, surface topography and<br />tribological behavior. Nanolayered and nanocomposite coatings are<br />characterized by compact nanocrystalline microstructure, while monolayer<br />TiAlN coatings have columnar structure with larger crystalline grains. By<br />increasing the number of rotational degrees from 1-fold to 3-fold size of<br />crystalline grains decreases and microstructure becomes more dense.<br />Therefore, nanolayered and nanocomposite coatings deposited with 2-fold<br />and 3-fold rotation are characterized by the highest hardness, highest<br />resistance to cracking, highest wear resistance and the smoothest surface<br />topography.</p>

Recently, powders of the size d (0.1 μm < d < 10 μm) have been referred to ultrafine particles. The particle shape considered is assumed to be a sphere of the diameter d. The handling of powders is of great importance for processing of pharmaceuticals, cement, chemicals and other products. Most of these technological processes involve powder compaction, storage, transportation, mixing, etc, therefore, understanding of the fundamentals of particles interaction behaviour is very essential in the design of machines and equipment as well as in powder technology, cleaning of environment and other areas. The dynamic behaviour of particulate systems is very complicated due to the complex interactions between individual particles and their interaction with the surroundings. Understanding the underlying mechanisms can be effectively achieved via particle scale research. The problem of a normal contact may be resolved in a number of ways. In spite of huge progress in experimental techniques, direct lab tests with individual particles are still rather time-consuming and expensive. The interaction of particles as solid bodies is actually a classical problem of contact mechanics. In the case of ultrafine particles, the reduction of the particle size shifts the contact zones into the nanoscale or subnanoscale. Thus, steadily increasing contribution of adhesion has to be considered in the development of the physically correct constitutive models and numerical tools. Consequently, it may... [to full text] / Ultrasmulkios dalelės yra šiuolaikinės chemijos, farmacijos, maisto ir kitų pramonės šakų produktų sudėtinė dalis. Tiriant pramoninius technologinius procesus, neišvengiamai reikalingos teorinės žinios apie ultrasmulkių dalelių elgseną. Išsamus supratimas įmanomas tik atlikus įvairius tyrimus. Pastaruoju metu milteliai, klasifikuojami kaip ultrasmulkios (0,1 < d < 10 μm) dalelės, imti plačiai naudoti pramoniniuose procesuose, todėl suprasti ultrasmulkių dalelių elgsenos fundamentalumą miltelių technologijoje yra labai svarbu. Ultrasmulki dalelė yra itin maža, todėl su ja atlikti fizinį eksperimentą, kuris reikalauja specialios įrangos bei žinių, labai sunku. Tokiu atveju dažniausiai naudojamas skaitinis eksperimentas, kurį galima atlikti virtualiai. Skaitinio eksperimento metu yra tiriamos dinaminės ultrasmulkios dalelės savybės bei sprendžiamas dinaminis uždavinys. Taikant skaitinius modelius bei dalelės judėjimą aprašančias jėgų lygtis, naudojami sąveikos modeliai, apimantys adhezinę, klampią, tamprią bei tampriai plastinę sąveikas. Mikroskopinis adhezinės sąveikos modeliavimas – aktualus mechanikos mokslo uždavinys. Taikant sąveikos modelius, svarbu pritaikyti ir diskrečiųjų elementų metodą, kadangi, norint aprašyti dalelių elgseną, visų pirma reikia su-vokti ir aprašyti dalelės modelį. Dalelės elgsenos skaitiniam modeliavimui siūlomi teoriniai modeliai leidžia tirti dalelės sąveiką su dalele ar tampria puserdve bei sąveikos dinamiką. Šie modeliai galėtų būti pritaikyti... [toliau žr. visą tekstą]