Stabilizacija holesteričnih modrih faz z nanodelci in nematski kalorični pojavi pod vplivom zunanjih polj

The doctoral dissertation is composed of two contently completed parts, with one common thing - liquid crystals. In both parts we are observing the order o liquid crystal molecules, leading to interesting and applicative properties. In the first part, the experimental results from various techniques are demonstrating the stabilization of cholesteric liquid crystal blue phases in liquid crystals doped with various functionalized nanoparticles. The second part presents some first direct experimental studies of the elastocaloric effect in side-chin and main-chain liquid crystal elastomers. In this part the nemato- and smecto-caloric effects, induced by external mechanical field, are presented. Specifically, in the first part the stabilization of different blue phases such as Blue Phase I (BPI), II (BPII) and III (BPIII) is studied by addition of the various types of nanoparticles (NPs) to the cholesteric liquid crystal (LC). Initial studies exploiting the spherical CdSe, CdSSe and gold nanoparticles demonstrate the stabilization of the disordered BPIII phase. The concentration-temperature phase diagram demonstrates widening of the BPIII with increasing concentration of spherical nanoparticles. It is found that different types of spherical nanoparticles with different core, size and functionalization always stabilize better the disordered BPIII phase as long the size of nanoparticles remains smaller or proportional to the disclination defect-line core size. In our research the platelet and rod nanoparticles were used to stabilize blue phase temperature range, since the theoretical prediction of better stabilization of blue phases with anisotropic nanoparticles were made and only spherical nanoparticles were used before. Polarized optical microscopy (POM) and high-resolution calorimetry experiments exploring the addition of platelet nanoparticles show a completely different picture than in the case of spherical nanoparticles. In contrast to spherical nanoparticles and quantum dots, which broaden the range of amorphous BPIII, the strongly anisotropic nanoparticles such as the platelet NPs and nanorods of different core, size and functionalization stabilize almost exclusively the cubic BPI. A theoretical model describing the BPs stabilization mechanisms is presented, based on the Landau-de Gennes phenomenological approach. In the case of spherical NPs, two mechanisms, the Defect Core Replacement (DCR) and the saddle-splay elasticity mechanism seem to play major role in stabilizing the disordered BPIII phase. In the case of anisotropic NPs, the third Adaptive Defect Core Targeting (ADCT) mechanism related to the energy penalty, due to disruption of the disclination core-surrounding order, represents an additional driving force of NPs into the cores of disclination lines. Similarly to what was found in the stabilization of the TGB$_A$ phase, the reduction of disclination defect-lines’ fluctuations caused by the formation of heavy anisotropic NPs’ clusters in their cores can also play an important role in stabilizing both BPI and BPIII. In the second part of the doctoral thesis the elastocaloric effect in liquid crystal elastomers is studied by a direct experimental technique. In recent years caloric effects, such as magnetocaloric effect, electrocaloric effect and mechanocaloric effect, attracted significant attention due to their applications in new, environmental friendly heat-management devices such as air conditioning devices, coolers and heat pumps. In the group of mechanocaloric effects belong barocaloric effect and elastocaloric effect (eCE). So far, the best elastocaloric response, exceeding a temperature change of 40 K, was achieved in shape memory alloy wires. However, the significant stress field required in those experiments, ~1 GPa, presents significant challenge for cooling applications. In this thesis, the elastocaloric effect in soft materials is explored. Such soft materials that need several order of magnitude lower stress field (closer to 1 MPa) are liquid crystal elastomers (LCEs). Direct measurements of the elastocaloric effect presented in this thesis demonstrate the existence of significant eCE in main-chain LCEs near the nematic transition. The simple Landau-de Gennes phenomenological model is presented, capturing most of the observed features of eCE. It is deduced that best eCE is achieved in LCEs engineered in such a way to sustain large thermomechanical response and to have large latent heat at the nematic phase transition, which greatly enhances the eCE.Doktorska disertacija je sestavljena iz vsebinsko dveh zaključenih celot, ki so jima skupni tekoči kristali. V obeh delih na različne načine opazujemo urejanje tekočekristalnih molekul, ki dajo v različnih primerih zanimive in aplikativne lastnosti. V prvem delu doktorske disertacije so predstavljeni rezultati meritev opravljenih z različnimi merilinimi tehnikami, ki prikazujejo stabilizacijo holesteričnih modrih faz z različnimi funkcionaliziranimi nanodelci. V drugem delu je predstavljeno nekaj neposrednih meritev elastokaloričnega efekta v glavno-verižnem tekočekristalnem elastomeru. Predstavljen je nematski kalorični pojav, ki je induciran z zunanjim mehanskim poljem. Če povzamem bolj natančno, je v prvem delu predstavljena raziskava stabilizacije različnih holesteričnih modrih faz, kot so modra faza I (BPI- ang. blue phase I), modra faza II (BPII) in modra faza III (BPIII), z dodajanjem različnih nanodelcev v holesterični tekoči kristal (TK). V prvih študijah se je raziskovalo predvsem stabilizacijo modrih faz z mešanicami kiralnih tekočih kristalov s sferičnimi nanodelci in kvantnimi pikami, kot so CdSe, CdSSe in zlati nanodelci. Fazni diagrami temperaturnih prehodov v odvisnosti od koncentracije nanodelcev v TK z dodanimi različnimi tipi sferičnih nanodelcev z različnimi jedri, velikostmi in funkcionalizacijo kažejo stabilizacijo BPIII. To velja vsaj dokler so delci manjše ali podobne velikosti kot jedro disklinacijskih linij. V nadaljni raziskavi pa smo se osredotočili na ploščate in paličaste nanodelce in njihov vpliv na širino območja posameznih modrih faz, saj so bile predstavljene teoretične simulacije, ki so predpostavljale boljšo stabilizacijo z dodajanjem anizotropnih nanodelcev, poleg tega pa taki nanodelci še niso bili uporabljeni v študijah pred tem. Rezultati kalorimetrije visoke ločljivosti in mikroskopije s prekrižanimi polarizatorji so pokazali, da funkcionalizirani anizotropni nanodelci nekoliko drugače stabilizirajo območje modrih faz. V primerjavi s sferičnimi in kvantnimi pikami, ki bolj stabilizirajo amorfno BPIII, nanopalčke in ploščati nanodelci z različnimi jedri, velikostmi in funkcinalizacijo večinoma bolj stabilizirajo bolj urejeno BPI. Predstavljen je teoretični model, ki je osnovan na Landau-de Gennesovem fenomenološkem pristopu, v katerem sta predstavljena dva mehanizma. Prvi DCR (ang. defect core replacement) sloni na zamenjavi tekočega kristala v jedru defekta z nanodelcem, medtem ko je drugi povezan z elastično deformacijo - sedlastim upogibom. Kaže, da ta dva mehanizma igrata veliko vlogo pri stabilizaciji modrih faz. Pomemben, še posebej v primeru večjih anizotropnih nanodelcev, je tudi tretji mehanizem ADCT (ang. adaptive defect core targeting), ki je povezan z energijsko izgubo zaradi motnje, ki jo delec povzroči okrog jedra disklinacijske linije. Ta mehanizem tako omogoči, da delec lažje ostane v jedru disklinacijske linije. Podobno kot je bilo ugotovljeno pri stabilizaciji TGB faz, nastanek težkih anizotropnih skupkov nanodelcev v jedru defektov zmanjša fluktuacije disklinacijskih defektnih linij in tako prispeva k stabilizaciji tako BPI kot tudi BPIII modre faze. V drugem delu so predstavljene neposredne meritve elastokaloričnega (eK) pojava v tekočekristalnih elastomerih. Kalorični pojavi, kot so magnetokalorični, elektrokalorični in mehanokalorični so v zadnjih letih pridobili veliko zanimanje zaradi njihove uporabe v novih, okolju prijaznih grelnih, hladilnih in klimatskih napravah. Med mehanokalorčne spadata barokalorični in elastokalorični. Slednji je najbolj raziskan v kovinah z oblikovnim spominom, v katerih so izmerili spremembo temperature do 40 K. Ker pa je v teh materialih potrebna mehanska napetost večja od 1 GPa, je njihova uporaba v hladilnih napravah povezana z velikimi izzivi. V tej tezi raziskujemo elastokalorični pojav v mehkih materialih, kot so tekočekristalni elastomeri (TKE), pri katerih je dovolj že nekaj redov manjša mehanska napetost (okrog 1 MPa) za vzbujanje eK pojava. Neposredne meritve elastokaloričnega pojava so potrdile, da obstaja merljiv eK pojav v okolici tekočekristalnega faznega prehoda v glavno-verižnih tekočekristalnih elastomerih. Preprost Landau-de Gennesov model opiše večino opaženih lastnosti eK pojava. Raziskave so pokazale, da pričakujemo največji eK pojav v TKE materialih, ki so pripravljeni tako, da imajo pri nematskem prehodu velik termomehanski odziv in veliko latentno toploto, ki dodatno ojača eK odzivnost

Anatomski in ekofiziološki odzivi puhastega hrasta (Quercus pubescens Willd.) na vsebnost vode v tleh v submediteranskem fitogeografskem območju Slovenije

Intra-annual variations in leaf development, radial growth (including the secondary phloem part), sap flow and non-structural carbohydrates (NSCs) have been rarely studied in deciduous trees from drought-prone environments. In order to better understand the chronological order and temporal course of these processes, we monitored leaf phenology, xylem and phloem formation (in different tree parts), sap flow (HRM method), variations in NSC amounts and relationship between various wood-anatomical parameters and climatic factors in Quercus pubescens Willd. from Podgorski Kras in Slovenia during study period 2014–2016. For this purpose two research areas (RA) were selected, where at RA2 two adjacent plots differing in bedrock and soil type (flysch with eutric cambisol, high water retention - Flimestone with rendzic leptosol, low water retention - L) were sampled. We found that initial earlywood vessels were fully lignified and ready for water transport before bud opening at the beginning of April. Buds started to open in the second half of April and full leaf unfolding occurred by the end of May. Sap flow was increasing contemporarily with leaf development and LAI values. In the initial three weeks of radial growth, phloem growth preceded that of xylem. Cambial cell production was one month longer at the stem base than in branches. In addition, the xylem ring was wider than the phloem ring in all three parts. The amount of NSCs significantly differed among the tissue parts and sampling dates but not between the plots. Starch amounts were the highest in xylem and the amounts of free sugars were highest in inner phloem + cambium. Trees on F were more buffered against drier hydroclimatic conditions due to a higher availability of soil water. In the period of severe drought, sap flow density in trees growing on L was decoupled from the changes of vapour pressure deficit, due to increased employment of water conservation strategies (decreases in stomatal conductance). This was further translated into stomatal limitation of photosynthesis and contributed to reduced radial stem growth that revealed smaller yearly xylem increments in L trees and anatomical acclimations of conductive tissues, supporting/preserving trees\u27 hydraulic function. Xylem ring width, early- and latewood widths, diameter, area and number of earlywood vessels were mainly related to temperature. Our study confirmed that the temporal sequence of leaf development and radial growth are not contemporary. Soil water availability substantially influenced secondary growth in the stem, whereas NSC amounts seemed to be less affected. It has been demonstrated that latewood width and earlywood vessel characteristics are promising wood-anatomical parameters containing complementary information on the impact of weather conditions on radial growth. We concluded that climate is not the only driver for radial growth of Q. pubescens at the selected locationssoil type with respect to water retention potential is also important environmental feature that needs to be considered in wood formation studies and growth models in the future.Medletna dinamika v razvoju listov, debelinski rasti (vključno z razvojem sekundarnega floema), ksilemskem toku vode in količinah nestrukturnih ogljikovih hidratov (NOH) je redko preučevana pri listavcih v okolju, ki je izpostavljeno suši. Z namenom boljšega razumevanja kronološkega zaporedja in časovnega poteka teh procesov smo spremljali fenologijo listov, nastanek ksilema in floema (v različnih delih drevesa), ksilemski tok vode (HRM metoda), razporeditev NOH in povezanost med različnimi lesno-anatomskimi parametri in podnebnimi dejavniki pri puhastem hrastu (Quercus pubescens Willd.) na Podgorskem Krasu (JZ Slovenija) v obdobju 2014-2016. V ta namen smo izbrali dva raziskovalna območja (RO), kjer smo na RO2 vzorčili dve bližnji ploskvi, ki sta se razlikovali v matični podlagi in tipu tal (evtrična rjava tla na flišu, visoko zadrževanje vode - Frendzina na apnencu, slaba sposobnost zadrževanja vode - L). Ugotovili smo, da so bile prve traheje v ranem lesu popolnoma lignificirane in pripravljene za transport vode pred odpiranjem brstov na začetku aprila. V drugi polovici aprila so se brsti začeli odpirati in polno olistanje dreves je nastopilo konec maja. Ksilemski tok vode je naraščal sočasno z razvojem listov in vrednostmi LAI. V prvih treh tednih debelinske rasti je rast floema potekala pred rastjo ksilema. Začetek in konec nastanka kambijevih celic sta bila sinhronizirana na obeh lokacijah v vejah, vendar sta bila različna v deblu (za mesec daljše). Ksilemski prirastek v deblu in v vejah je bil širši od floemskega prirastka. Količina NOH se je bistveno razlikovala med posameznimi tkivi in datumi vzorčenja, ne pa med ploskvama. Količina škroba je bila najvišja v ksilemu in količina topnih sladkorjev v notranjem floemu + kambiju. Hrasti na mokrem rastišču F so bili bolj zaščiteni pred sušnimi hidroklimatskimi razmerami. V obdobju močne suše, ksilemski tok vode v hrastih na L ni bil odvisen od sprememb v deficitu tlaka vodne pare, ampak je na njegovo dinamiko vplivala povečana uporaba strategij hrasta za ohranjanje vode, kot je zmanjšanje stomatalne prevodnosti. To je vplivalo na omejevanje fotosinteze in prispevalo k zmanjšanju debelinske rasti debla. Anatomske študije so pokazale manjše letne prirastke ksilema pri hrastih s ploskve L in anatomske aklimacije prevodnih tkiv, ki podpirajo/ohranjajo hidravlično funkcijo dreves. Končna širina branike, širina kasnega in ranega lesa ter premer, površina in število trahej ranega lesa so bili povezani predvsem s temperaturo. Potrdili smo, da časovno zaporedje razvoja listov in debelinske rasti ni usklajeno. Razpoložljivost vode v tleh je bistveno vplivala na sekundarno rast v deblu, medtem ko na količine NOH ni bilo zaznati vpliva. Ugotovili smo, da so širina kasnega lesa in značilnosti trahej ranega lesa primerni lesno-anatomski parametri, ki vsebujejo komplementarne informacije o vplivu vremenskih razmer na debelinsko rast. Potrdili smo, da podnebje ni edino, ki vpliva na debelinsko rast puhastega hrasta na izbranih lokacijah. Talni tip z vidika sposobnosti zadrževanja vode je tudi pomembna okoljska značilnost, ki jo je potrebno upoštevati pri preučevanju rasti in funkcionalnosti dreves v različnih okoljskih razmerah ter modelih debelinske rasti v prihodnosti

Continuity of monotone functions

summary:It is shown that a monotone function acting between euclidean spaces $R^n$ and $R^m$ is continuous almost everywhere with respect to the Lebesgue measure on $R^n$

Functionalization of textile materials with stimulisponsive microgel:A study of liquid management properties

The aim of the research presented in this chapter was to prepare cotton fabrics with "intelligent" liquid management properties by functional finishing with stimuli-responsive microgel. The targeted use of these fabrics is in performance apparel, where the added value of controlled ("on-demand") liquid management could enable the transformation of cotton into an advanced material. Functional finishing using the surface modification approach is expected to introduce advanced properties to the material without impairing its intrinsic properties, which currently make cotton the most widely used textile material

Stable isotope (C, O, S) systematics of the mercury mineralization at Idrija, Slovenia: constraints on fluid source and alteration processes

The world-class Idrija mercury deposit (western Slovenia) is hosted by highly deformed Permocarboniferous to Middle Triassic sedimentary rocks within a complex tectonic structure at the transition between the External Dinarides and the Southern Alps. Concordant and discordant mineralization formed concomitant with Middle Triassic bimodal volcanism in an aborted rift. A multiple isotopic (C, O, S) investigation of host rocks and ore minerals was performed to put constraints on the source and composition of the fluid, and the hydrothermal alteration. The distributions of the δ13C and δ18O values of host and gangue carbonates are indicative of a fracture-controlled hydrothermal system, with locally high fluid-rock ratios. Quantitative modeling of the δ13C and δ18O covariation for host carbonates during temperature dependent fluid-rock interaction, and concomitant precipitation of void-filling dolomites points to a slightly acidic hydrothermal fluid (δ13C≈−4‰ and δ18O≈+10‰), which most likely evolved during isotopic exchange with carbonates under low fluid/rock ratios. The δ34S values of hydrothermal and sedimentary sulfur minerals were used to re-evaluate the previously proposed magmatic and evaporitic sulfur sources for the mineralization, and to assess the importance of other possible sulfur sources such as the contemporaneous seawater sulfate, sedimentary pyrite, and organic sulfur compounds. The δ34S values of the sulfides show a large variation at deposit down to hand-specimen scale. They range for cinnabar and pyrite from −19.1 to +22.8‰, and from −22.4 to +59.6‰, respectively, suggesting mixing of sulfur from different sources. The peak of δ34S values of cinnabar and pyrite close to 0‰ is compatible with ore sulfur derived dominantly from a magmatic fluid and/or from hydrothermal leaching of basement rocks. The similar stratigraphic trends of the δ34S values of both cinnabar and pyrite suggest a minor contribution of sedimentary sulfur (pyrite and organic sulfur) to the ore formation. Some of the positive δ34S values are probably derived from thermochemical reduction of evaporitic and contemporaneous seawater sulfate

Sulfur isotope variations from orebody to hand-specimen scale at the Mežica lead-zinc deposit, Slovenia: a predominantly biogenic pattern

The Mississippi Valley-type (MVT) Pb-Zn ore district at Mežica is hosted by Middle to Upper Triassic platform carbonate rocks in the Northern Karavanke/Drau Range geotectonic units of the Eastern Alps, northeastern Slovenia. The mineralization at Mežica covers an area of 64km2 with more than 350 orebodies and numerous galena and sphalerite occurrences, which formed epigenetically, both conformable and discordant to bedding. While knowledge on the style of mineralization has grown considerably, the origin of discordant mineralization is still debated. Sulfur stable isotope analyses of 149 sulfide samples from the different types of orebodies provide new insights on the genesis of these mineralizations and their relationship. Over the whole mining district, sphalerite and galena have δ 34 S values in the range of -24.7 to -1.5‰ VCDT (-13.5 ± 5.0‰) and -24.7 to -1.4‰ (-10.7 ± 5.9‰), respectively. These values are in the range of the main MVT deposits of the Drau Range. All sulfide δ 34 S values are negative within a broad range, with δ 34 S pyrite <δ 34 S sphalerite <δ 34 S galena for both conformable and discordant orebodies, indicating isotopically heterogeneous H2S in the ore-forming fluids and precipitation of the sulfides at thermodynamic disequilibrium. This clearly supports that the main sulfide sulfur originates from bacterially mediated reduction (BSR) of Middle to Upper Triassic seawater sulfate or evaporite sulfate. Thermochemical sulfate reduction (TSR) by organic compounds contributed a minor amount of 34S-enriched H2S to the ore fluid. The variations of δ 34 S values of galena and coarse-grained sphalerite at orefield scale are generally larger than the differences observed in single hand specimens. The progressively more negative δ 34 S values with time along the different sphalerite generations are consistent with mixing of different H2S sources, with a decreasing contribution of H2S from regional TSR, and an increase from a local H2S reservoir produced by BSR (i.e., sedimentary biogenic pyrite, organo-sulfur compounds). Galena in discordant ore (-11.9 to -1.7‰; -7.0 ± 2.7‰, n = 12) tends to be depleted in 34 S compared with conformable ore (-24.7 to -2.8‰, -11.7 ± 6.2‰, n = 39). A similar trend is observed from fine-crystalline sphalerite I to coarse open-space filling sphalerite II. Some variation of the sulfide δ 34 S values is attributed to the inherent variability of bacterial sulfate reduction, including metabolic recycling in a locally partially closed system and contribution of H2S from hydrolysis of biogenic pyrite and thermal cracking of organo-sulfur compounds. The results suggest that the conformable orebodies originated by mixing of hydrothermal saline metal-rich fluid with H2S-rich pore waters during late burial diagenesis, while the discordant orebodies formed by mobilization of the earlier conformable mineralizatio