56 research outputs found
Literatura za ispit iz kolegija "Suvremena druŔtvena pitanja u SAD" i "Modern American Drama", postdiplomski studij amerikanistike, Dubrovnik, 1988
Literatura za postdiplomski studij amerikanistike u Dubrovniku, 1988., za ispite iz kolegija "Suvremena druÅ”tvena pitanja u SAD" prof. Ognjena ÄaldaroviÄa, i kolegija "Modern American Drama" prof. Ivana V. MatkoviÄa
Literatura za ispit iz kolegija "Suvremena druŔtvena pitanja u SAD" i "Modern American Drama", postdiplomski studij amerikanistike, Dubrovnik, 1988
Literatura za postdiplomski studij amerikanistike u Dubrovniku, 1988., za ispite iz kolegija "Suvremena druÅ”tvena pitanja u SAD" prof. Ognjena ÄaldaroviÄa, i kolegija "Modern American Drama" prof. Ivana V. MatkoviÄa
Ispitivanje optiÄkih osobina grafena pomoÄu spektroskopske elipsometrije
The dissertation addresses the problem of retrieving the optical properties of
graphene in the visible and UV ranges using ellipsometry. Additionally, it is demonstrated
how changes in these properties could be related to various fabrication aspects
including the transfer process and the interaction of graphene with various
substrates. Besides their importance in advancing the fundamental understanding
of optical properties of graphene, these results could be used for implementation of
ellipsometry as a quality control in graphene-based technologies. As these technologies
expand, it will be increasingly important to have tools which are able not only
to detect the presence of a graphene layer but also to give information of subtle
changes in the properties of these ultra thin films. Ellipsometry, due to its numerous
advantages, is most definitely one of the techniques that will be employed as a
quality control tool in the future mass production of graphene.
In the dissertation optical properties of graphene were studied using spectroscopic
ellipsometry and null spectroscopic imaging ellipsometry techniques. The studied
samples were atomically thin layers of graphene synthesized by micromechanical
exfoliation and chemical vapor deposition. These samples were supported by various
substrates, such as silicon wafers with thin SiO2 films, transparent (sapphire) and
metallic (gold) substrates. An importance of using corroborated measurements for
building up an appropriate optical models has been shown as well.
Optical parameters of graphene have been retrieved using a point-by-point inversion
process, and afterwards parameterized by a dielectric function model. A
proposed parametrization function of grapheneās complex refractive index is based
on a Fano resonant profile. This model has only four fitting parameters, and their
values can be easily related to the properties of the M-point exciton that causes the
red shift of the prominent absorption peak in the UV. Various set of model paramv...Disertacija se bavi problemom merenja optiÄkih osobina grafena u vidljivom i
ultraljubiÄastom delu spektra. Takodje, u disertaciji demonstrirano je kako se
promene optiÄkih osobina mogu povezati sa praĀ“cenjem procesa sinteze, transfera, kao
i interakcije grafena sa supstratom. Osim znaÄaja za fundamentalno razumevanje
optiÄkih osobina grafena, prikazani rezultati mogu se iskoristiti za implementaciju
elipsometrije kao tehnike za kontrolu kvaliteta u novim tehnologijama zasnovanim
na grafenu. Sa daljim razvojem ovih tehnologija, neophodno je imati adekvantne
merne tehnike koje nisu osetljive samo na prisustvo mono-atomskog sloja, veÄ su u
stanju da pouzdano detektuju fine promene u osobinama ovih ultra tankih filmova.
Zbog svojih brojnih prednosti, elipsometrija je zasigurno jedna od tehnika koja Äe
biti koriÅ”Äena za kontrolu kvaliteta, kao i procesa sinteze u buduĀ“cim tehnologijama
za masovnu proizvodnju grafena.
U disertaciji optiÄke osobine grafena su merene pomoĀ“cu tehnika nulirajuÄe i spektroskopske
elipsometrije. Ispitivani su uzorci monoatomskih slojeva grafena, sintetisanih
pomoÄu mikromehaniÄke eksfolijacije i depozicije iz gasne faze. Takodje,
istaknut je znaÄaj koriÅ”Äenja korelacionih merenja za formiranje optiÄkih modela i
interpretaciju elipsometarskih merenja grafena.
OptiÄke konstante grafena su dobijene pomoÄu matematiÄke inverzije, a zatim
parametrizovane pomoÄu modela dielektriÄne funkcije grafena. Predloženi model
kompleksnog indeksa prelamanja grafena je zasnovan na Fano rezonantnom profilu.
Ovaj model ima samo Äetiri parametra Äije se vrednosti mogu jednostavno povezati
sa osobinama eksitona u M-taÄki, koji izaziva crveni pomeraj apsorpcionog maksimuma
u ultraljubiÄastom delu spektra. RazliÄiti parametri modela dielektriÄne
funkcije su prezentovani u disertaciji. Ovi parametri opisuju razliÄite optiÄke osobine
grafena koje su rezultat interakcije izmedju grafena i njegove okoline, eksternih
v
Kinetics and mechanism of sphalerite leaching by sodium nitrate in sulphuric acid solution
Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90Ā°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90Ā°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism
Crystal Structure of Citrobacter freundii Asp214Ala Tyrosine Phenollyase Reveals that Asp214 is Critical for Maintaining a Strain in the Internal Aldimine
Tyrosine phenol-lyase (TPL) is a pyridoxal-5ā²-phosphate (PLP) dependent enzyme which catalyzes Ī²-elimination of L-tyrosine. In the holoenzyme the protonated pyridinium N1 atom of the PLP cofactor is hydrogen-bonded to the side chain of Asp214. Here we report the X-ray structure of C. freundii D214A TPL determined at 1.9 Ć
resolution. Comparison with the structure of the wild-type TPL shows that the D214A replacement induced significant conformational reorganization in the active site leading to its partial closure. Significantly, in D214A TPL the strain in the internal aldimine is completely released and the pyridine N1 atom of PLP is deprotonated. These observations explain the considerably reduced activity of the D214A TPL towards its substrates [T. V. Demidkina et al., Biochim. Biophys. Acta, Proteins Proteomics 1764 (2006) 1268ā1276]. The reported structure reveals that Asp214 is critical for maintaining the strain in the internal aldimine. We argue that this strain is used by the enzyme to accelerate the transaldimination reaction, the first step in the enzymatic catalysis.(doi: 10.5562/cca1915
Preparation and Crystal Data of N-(2-hydroxyethyl) taurine, HOCH2CH2NHCH2CH2SOJH
Taurine is a constituent of the bile acids. Since the knowledge of the
crystal structure of taurine was important in understanding the biological
role of the molecule, structural work on this compound was carried out by
several authors1- 3. The last study3 has established that taurine possesses the zwitterion configuration with structural formula NHa+-CH2- CH2-S00-
Istraživanja dekantacije Ā»crvenog muljaĀ« drniÅ”kog boksita
Upotrebom drniskog boksita kod alkalnog rascinjavanja po Bayer-u nastupaju znatne potreskoce. One sastoje u tome, sto se nakon reakcije u autoklavu i razrijedivanja reakcione smjese talozenja crvenog mulja odvija suvise polagano i neravnomjerno, zbog cega se znatno smanjuje produkcija
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