Electronic and optical properties of defformed graphitic and helical nanobutes

Motivacija U ovoj tezi su prezentovani rezultati iscrpne analize elektronskih i optičkih osobina dva tipa ugljeničnih nanotuba. Prvi deo se odnosi na homogeno deformisane jednoslojne ugljenične nanotube (tj. grafitne nanotube), dok su u drugom delu rezultati za nedeformisane i podužno istegnute helikalne ugljenične nanotube. Konfiguracije nedeformisanih grafitnih nanotuba su dobro poznate: sa izuzetkom tuba jako malog dijametra, odgovara grafenskoj ravni urolovanoj na specifičan način. Sa druge strane, možemo smatrati da su helikalne nanotube rezultat periodičnog umetanja sedmougaonih i petougaonih defekata u grafensku rešetku, što prouzrokuje njihovu karakterističnu helikalnu morfologiju. Od svih nanomaterijala baziranih na ugljeniku ove nanotube imaju najsloženiju i najraznovrsniju strukturu. Pored tri ”globalna” geometrijska parametra, koje je moguće direktno meriti u ogledima, postoje i ”lokalni” parametari koji opisuju položaj defekata unutar monomera. Zbog toga se kod ovog tipa tuba očekuju i raznovrsnije elektronske osobine. U tezi je razmotren uticaj globalnih i lokalnih parametara, kao i moguće modifikacije elektronskih osobina pomoću mehaničkih napona. Kod nanotuba efekti deformacionog sprezanja na fizičke osobine nisu do sada sistematski analizirane. Za uspešnu primenu u različitim nano-elektromehaničkim uređajima detalno poznavanje efekata deformacionog sprezanja je od velike važnosti. Tendencija smanjivanja mehaničkih i elektronskih uređaja ka nanometarskoj skali, nameće potrebu za izradom efikasnih senzora za merenje i kontrolu ponašanja odgovaraju ćih nanouređaja. Postojeće mikrosenzore je nemoguće skalirati na nanodimenzije, a da ne dođe do drastičnog smanjenja dinamičkog opsega senzora. U cilju prevazilaženja prepreke nametnute skaliranjem 3D materijala, potrebno je razmotriti mogućnosti primene inherentnih 2D materijala, posebno onih baziranih na kompozitnim filmovima od grafitnih nanotuba kod kojih efekti skaliranja daleko manje utiču na promenu karakteristika...Motivation Results of the comprehensive study of electronic and optical properties of two types of carbon nanotubes are presented in this thesis. First part considers homogenously deformed single-wall carbon nanotubes(i.e. graphitic nanotubes), while the second one contains results for non-deformed and uniaxially strained helically coiled carbon nanotubes. Configurations of non-deformed single-wall carbon nanotubes are well known: with exception of extremely narrow tubes, it corresponds to specifically rolled up graphene plane. On the other hand, helically coiled carbon nanotubes can be understand as the result of periodic insertion of heptagonal and pentagonal defects in graphene lattice which results in their characteristic helical morphology. Among all carbon based nanomaterials, these tubes have the most complex and most diverse structures. Besides three ”global” geometric parameters of helical coil, which can be directly measured in experiments, there are a number of ”local” parameters that describe position of defects within the monomer. Therefore, more diverse electronic properties are expected for these type of tubes. Influence of global and local parameters and possible modification of electronic properties by mechanical stress are addressed in this research study. For the nanotubes effects of strain coupling on its physical properties has not been systematically analyzed. For successful application in various nano-electromechanical devices, detailed knowledge of effects of strain coupling on electronic and optical properties are of the most importance. The tendency of decreasing mechanical and electronic devices to the nanometer scale, imposes need to develop effective sensors to measure and control the behavior of various nanodevices. However, without a drastic reduction of the basic characteristics of the existing micro-sensors it is impossible to scale them down to nanodimension. In order to overcome the barriers imposed by scaling of 3D materials, it is necessary to consider the possible application of inherent 2D materials, especially those based on composite films of carbon nanotubes where the change in characteristics are far less affected by scaling..

Allelopathic effects of Chenopodium murale L. hairy roots in vitro

Korenov sistem C. murale produkuje i luči hemijske materije koje imaju alelopatsku aktivnost. Proučavanje efekata na druge organizme, kao i izolovanje i karakterizacija metabolita koji su izlučeni iz korenova u zemljište je veoma kompleksan proces. Zbog toga je cilj ovog istraživanja bio uspostavljanje kulture transformisanih korenova C. murale in vitro, kao novog sistema pogodnog za izučavanje alelopatskog efekta. Transgeni korenovi su indukovani pomoću Agrobacterium rhizogenes A4M70GUS na eksplantatima korenova, kotiledona, listova i internodija klijanaca C. murale. Eksplantati korenova su imali najveću efikasnost transformacije (11,1%). Uspostavljeni su klonovi transformisanih korenova različite morfologije i potencijala rasta koji se gajenjem (subkultivisanjem) u tečnom MS medijumu održavaju više od dve godine. Potvrda transformacije ovih klonova je urađena pomoću PCR, RT–PCR i histohemijske GUS analize. Nije ustanovljena razlika u prisustvu rol gena među klonovima. Ispitivan je alelopatski efekat tečnih medijuma u kojima su rasli transformisani i netransformisani korenovi C. murale (fitotoksični medijum) na klijanje i rast klijanaca test biljaka arabidopsisa (Arabidopsis thaliana (L.) Heynh), pšenice (Triticum aestivum L.) i salate (Lactuca sativa L.). Kod sve tri test biljke ustanovljen je inhibitorni efekat na klijanje semena i rast klijanaca. Klonovi transformisanih klonova: R1 i R8, imali su najveći alelopatski potencijal. Kod test biljaka arabidopsisa i pšenice, koje su bile tretirane fitotoksičnim medijumima, praćena je ukupna aktivnost antioksidativnih enzima – katalaza, peroksidaza i superoksid dismutaza (spektrofotometrijski), kao i zastupljenost i aktivnost pojedinih izoformi navedenih enzima (elektroforetski). Aktivnost ovih enzima (izuzev katalaza kod arabidopsisa) bila je povećana kod klijanaca isklijavanih i gajenih na fitotoksičnim medijumima, što je u skladu sa aktiviranjem odbrambenih mehanizama u biljkama kada se one bile izlažu stresu (fitotoksinima, tj. alelohemikalijama). Fitotoksični medijumi različitih klonova transformisanih korenova dovodili su do različitog nivoa povećanja aktivnosti katalaza, peroksidaza i superoksid dismutaza kod različitih test biljaka...Root system produces and releases chemical compounds with allelopathic activity. Isolation and characterization of these metabolites, as well as investigation of their effects on other organisms, are very complicated processes. The aim of the present study was to initiate and establish Chenopodium murale L. transgenic hairy root in vitro culture system, as a new tool for allelopathic assays. Transgenic hairy roots were induced by Agrobacterium rhizogenes A4M70GUS from roots, cotyledons, leaves and internodes of C. murale seedlings. Roots were found to be the best target explants, providing transformation efficiency of up to 11.1%. Established 13 hairy root clones differed in their morphology and growth potential. The liquid culture system of characterized hairy root clones was maintained for over two years. Molecular characterization of these clones was carried out by PCR, RT-PCR and histochemical GUS analyses. No differences in rol gene presence were observed. We investigated allelopathic effect of wild-type and hairy root growth media (phytotoxic media) against germination and seedling development of Arabidopsis thaliana (L.) Heynh, wheat (Triticum aestivum L.) and lettuce (Lactuca sativa L.) test plants. The inhibitory potential varied depending on the test plant and hairy root clone. R1 and R8 clones had strong allelopathic effects. These results revealed that hairy roots as an independent system synthesize some bioactive substances with allelopathic activity and exude them into the growth medium. In test plants A. thaliana and wheat, after treatment with phytotoxic media, activity of different antioxidative enzymes (catalase, peroxidase and superoxide dismutase) were analyzed spectrophotometrically and electrophoretically. Activities of these antioxidative enzymes were higher in comparison to the control, except the catalase activity in A. thaliana, which was the same or lower. Phytotoxic media from different hairy root clones cause different changes in activities of catalases, peroxidases and superoxide dismutases in test plants..

Shungite – a carbon-mineral rock material: Its sinterability and possible applications

The paper presents results of the influence of mechanical activation of shungite, a carbon-mineral rock material rich in silica and carbon, on its sintering behaviour, and obtaining of pure SiC ceramics. The mechanical activation of the starting powder was performed in a high-energy ball mill in time intervals from 30 to 480 min. The phase composition of the starting powders and sintered samples was analysed by the X-ray diffraction method. The first traces of SiC were detected after sintering at 1350 °C for 2 h in an Ar atmosphere, along with traces of unreacted SiO2. The scanning electron microscopy was performed in order to determine changes in the microstructure. Sintering was performed at various temperatures for 2 h, in an Ar atmosphere and a vacuum. Dielectric properties of the sintered samples were measured in the frequency range from 1 to 500 MHz. The obtained results indicate that the sintered powder is a good candidate for applications as an absorber of electromagnetic waves in microwave engineering

Physiological and cell ultrastructure disturbances in wheat seedlings generated by Chenopodium murale hairy root exudate.

Chenopodium murale L. is an invasive weed species significantly interfering with wheat crop. However, the complete nature of its allelopathic influence on crops is not yet fully understood. In the present study, the focus is made on establishing the relation between plant morphophysiological changes and oxidative stress, induced by allelopathic extract. Phytotoxic medium of C. murale hairy root clone R5 reduced the germination rate (24% less than control value) of wheat cv. Nataša seeds, as well as seedling growth, diminishing shoot and root length significantly, decreased total chlorophyll content, and induced abnormal root gravitropism. The R5 treatment caused cellular structural abnormalities, reflecting on the root and leaf cell shape and organization. These abnormalities mostly included the increased number of mitochondria and reorganization of the vacuolar compartment, changes in nucleus shape, and chloroplast organization and distribution. The most significant structural changes were observed in cell wall in the form of amoeboid protrusions and folds leading to its irregular shape. These structural alterations were accompanied by an oxidative stress in tissues of treated wheat seedlings, reflected as increased level of H2O2 and other ROS molecules, an increase of radical scavenging capacity and total phenolic content. Accordingly, the retardation of wheat seedling growth by C. murale allelochemicals may represent a consequence of complex activity involving both cell structure alteration and physiological processes.This is a post-peer-review, pre-copyedit version of an article published in Protoplasma. The final authenticated version is available online at: [http://dx.doi.org/10.1007/s00709-018-1250-0

The war and its influence on the malignant tumors’ incidence

We have observed the incidence of malignant tumours among 254 patients of Osijek University Hospital in the pre-war period (1990-92) and 255 patients after the war (June 1992-93. After the war there has been a significant decrease of well differentiated malignant tumors incidence: 84 cases (33,07%) before the war, 30 cases (11,76%) after the war, however, there has been a significantly increased incidence of anaplastic tumours: 9 cases (3,54%) before the war, 21 cases (8,24%) after the war. There has been statistically significant increase of stomach, ovaries and testis malignant neoplasm incidence in the observed period (2=76,559, p<0,0001)