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Geometric unification of Higgs bundle vacua
Mirjam Cvetič, Jonathan J. Heckman, Thomas B. Rochais, Ethan Torres, Gianluca Zoccarato, 2020, izvirni znanstveni članek

Opis: Higgs bundles are a central tool used to study a range of intersecting brane systems in string compactifications. Solutions to the internal gauge theory equations of motion for the corresponding worldvolume theories of brans give rise to different low energy effective field theories. This has been heavily used in the study of M-theory on local G(2) spaces and F-theory on local elliptically fibered CalabiYau fourfolds. In this paper we show that the 3D N = 1 effective field theory defined by M-theory on a local spin(7) space unifies the Higgs bundle data associated with 4D N = 1 M- and F-theory vacua. This 3D system appears as an interface with finite thickness between different 4D vacua. We develop the general formalism of M-theory on such local spin(7) spaces and build explicit interpolating solutions. This provides a complementary local gauge theory analysis of a recently proposed approach to constructing spin(7) spaces from generalized connected sums.
Ključne besede: F-theory, Higgs, M-theory, field theories, spin spices
Objavljeno v DKUM: 23.10.2023; Ogledov: 429; Prenosov: 11
.pdf Celotno besedilo (1,06 MB)
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T-branes and G(2) backgrounds
Rodrigo Barbosa, Mirjam Cvetič, Jonathan J. Heckman, Craig Lawrie, Ethan Torres, Gianluca Zoccarato, 2020, izvirni znanstveni članek

Opis: Compactification of M-string theory on manifolds with G(2) structure yields a wide variety of 4D and 3D physical theories. We analyze the local geometry of such compactifications as captured by a gauge theory obtained from a three-manifold of ADE singularities. Generic gauge theory solutions include a nontrivial gauge field flux as well as normal deformations to the three-manifold captured by noncommuting matrix coordinates, a signal of T-brane phenomena. Solutions of the 3D gauge theory on a three-manifold are given by a deformation of the Hitchin system on a marked Riemann surface which is fibered over an interval. We present explicit examples of such backgrounds as well as the profile of the corresponding zero modes for localized chiral matter. We also provide a purely algebraic prescription for characterizing localized matter for such T-brane configurations. The geometric interpretation of this gauge theory description provides a generalization of twisted connected sums with codimension seven singularities at localized regions of the geometry. It also indicates that geometric codimension six singularities can sometimes support 4D chiral matter due to physical structure "hidden" in T-branes.
Ključne besede: Yang-Mills connections, spin(7), holonomy, bundles, metrics
Objavljeno v DKUM: 16.10.2023; Ogledov: 203; Prenosov: 12
.pdf Celotno besedilo (710,65 KB)
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Modeling, simulation, and verification of a Bounded Retransmission Protocol using Spin model checker and SpinRCP integrated development environment : master's thesis
Pero Buden, 2022, magistrsko delo

Opis: Simple Promela Interpreter (Spin) is a model checker that uses Protocol Meta Language (PROMELA) to describe systems. Unfortunately, PROMELA does not support any time constructs, limiting the implementation of a Bounded Retransmission Protocol (BRP) in Spin's integrated development environment called Spin Rich Client Platform (SpinRCP). In the master's thesis, we model, simulate, and verify four versions of BRP. The first two versions are modeled without a timer, and with the others we show two different ways to simulate timers in PROMELA. The tests we run will show the time and space complexity of verifying each version depending on the size of the file sent and the number of retries to send each chunk.
Ključne besede: model checker, Bounded Retransmission Protocol, Spin, SpinRCP, timer
Objavljeno v DKUM: 20.10.2022; Ogledov: 384; Prenosov: 32
.pdf Celotno besedilo (3,54 MB)

Design, Characterisation and Applications of Cellulose-Based Thin Films, Nanofibers and 3D Printed Structures : A Laboratory Manual
Tanja Pivec, Tamilselvan Mohan, Rupert Kargl, Manja Kurečič, Karin Stana-Kleinschek, 2021, drugo učno gradivo

Opis: The introduction of the Laboratory Manual gives the theoretical bases on cellulose and its derivatives, which are used as starting polymers for the preparation of multifunctional polymers with three different advanced techniques - spin coating, electrospinning and 3D printing. In the following, each technique is presented in a separate Lab Exercise. Each exercise covers the theoretical basics on techniques for polymer processing and methods for their characterisation, with an emphasis on the application of prepared materials. The experimental sections contain all the necessary information needed to implement the exercises, while the added results provide students with the help to implement correct and successful exercises and interpret the results.
Ključne besede: multifunctional polymers, polysaccharides, cellulose, electrospun, spin coating, 3D printing, nanofibers, thin films, multifunctional materials, laboratory manuals
Objavljeno v DKUM: 09.03.2021; Ogledov: 889; Prenosov: 23
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Spin-coating for optical-oxigen-sensor preparation
Polonca Brglez, Andrej Holobar, Aleksandra Pivec, Mitja Kolar, 2014, izvirni znanstveni članek

Opis: Thin-film oxygen sensors were prepared using the spin-coating technique, where a tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex (RuDPP) in various solvents and silicones deposited on different substrates was used for the sensor production. By changing the spin-coating set-up parameters, homogeneous sensor coatings and the optimum sensor response to oxygen were studied – the sensors were exposed to various concentrations of oxygen within the range from 0% to 100 %. During the presented study, the optimum results were obtained when a 150 µL of sensor solution was applied to a Dataline foil using silicone E4 and a chloroform solvent. A spin coater with the following three rotation stages was used: 750/700 r/min for 3 s, 300 r/min for 3 s and 150 r/min for 4 s. The spin-coating technique has several benefits: it is fast, easy to use and appropriate for low-volume operations. It allows modifications and preparations of several sensor series using the minimum reagent consumption. However, the disadvantage of this technique also has to be mentioned, namely, an uneven film thickness in the radial direction. The film thickness mainly depends on the experimental set-up (volume, rotation time and speed, solvent viscosity and evaporation). Spin coating as an alternative and very flexible technique for an oxygen-sensor preparation is suggested for the laboratory-scale work, where the majority of experimental data could be used when other new coating methods are also researched and implemented.
Ključne besede: optical sensors, spin coating, oxigen
Objavljeno v DKUM: 21.12.2015; Ogledov: 1786; Prenosov: 100
.pdf Celotno besedilo (254,63 KB)
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Matej Hribar, 2015, magistrsko delo

Opis: Namen magistrskega dela je bil priprava novih polisaharidnih materialov in njihova karakterizacija. V prvem delu smo preučevali homogeno reakcijo sililiranja hidroksietil celuloze (HEC) in homogeno reakcijo sililiranja hitina. Skupno smo opravili 9 sintez z uporabo različnih sililirnih sredstev in pri različnih reakcijskih pogojih. Nastale produkte reakcij smo analizirali z IR spektroskopijo in preverili topnost produktov v nekaterih organskih topilih. V drugem delu pa smo se ukvarjali s pripravo tankih filmov celuloze in njenih derivatov s pomočjo ''spin-coating'' tehnike ter kemijsko in površinsko karakterizacijo le-teh. Tanke filme smo pripravili iz raztopin celuloznega acetata (CA), etil celuloze (EC), trimetilsilil celuloze (TMSC) in dvokomponentnih mešanic v različnih razmerjih. Na eni ponovitvi filmov smo izvedli tudi postopek regeneracije. Pripravili smo tudi debelejše filme in njihove regenerirane ponovitve. V zadnjem delu smo izvedli karakterizacijo tankih filmov. Za pridobitev informacij o površinskih in kemijskih lastnostih tankih filmov smo izvedli meritve stičnega kota, opravili IR spektroskopijo, izvedli meritev adsorpcije različnih proteinov na pripravljene tanke filme s tehniko QCM-D in naredili topografske meritve s tehniko AFM. Na debelejših filmih smo izvedli le meritve stičnega kota. Z reakcijami sililiranja HEC smo uspešno sintetizirali želen produkt. V primeru sililiranja hitina želenega produkta nismo uspeli sintetizirati. Nastali produkti reakcij so v organskih topilih slabo topni oz. nabrekajo. Z analizo IR spektroskopije tankih filmov smo dokazali uspešno cepitev na predvideni vezi in nastanek –OH skupine po opravljenem postopku regeneracije. Zaradi nastanka novih –OH skupin po postopku regeneracije je postala površina bolj hidrofilna, kar smo dokazali z meritvami stičnega kota. Meritve adsorpcije proteinov so pokazale, da imajo hidrofobne površine večjo težnjo po ireverzibilni vezavi govejega serumskega albumina (BSA), medtem ko ima fibrinogen visoko afiniteto do adsorpcije na površino celuloznega acetata. Razviti materiali kažejo na potencialno uporabo na področju biomedicine, kot so na primer površine senzorjev ali pa biokompatibilne plasti, ki preprečujejo obraščanje.
Ključne besede: celuloza in celulozni derivati, hitin, sililiranje, tanki filmi, spin-coating, ATR-FTIR, stični kot, adsorpcija proteinov, QCM-D, AFM
Objavljeno v DKUM: 21.10.2015; Ogledov: 2131; Prenosov: 260
.pdf Celotno besedilo (4,68 MB)

Dejan Žalik, 2015, magistrsko delo

Opis: Globalni razvoj trga in hkratne spremembe v poslovnem okolju silijo podjetja, da se nenehno prilagajajo poslovnim in strukturnim spremembam. Ena izmed oblik prilagajanja spremembam so podjetni spin-offi. Poenostavljeno povedano gre za odsvojitev nezdravega dela podjetja od zdravih ali obratno oziroma izločitev tistega specifičnega dela podjetja, za katerega se pričakuje, da bo bolje posloval, če bo na svojem. Z analizo vzorca poslovnih spin-offov na globalni ravni iz obdobja štirinajstih let preverimo, ali takšne poslovne poteze v povprečju ustvarjajo vrednost za podjetja oziroma njihove lastnike. S pomočjo tržnih kapitalizacij različnih podjetij, ki predstavljajo vrednost podjetja v različnih trenutkih okoli dogodka, opazujemo, kakšen je razvoj vrednosti pred in po dogodku. V analizo vključimo tržne indekse in njihove vrednosti, ki naj bi predstavljali splošno gibanje gospodarskega okolja v omenjenem časovnem obdobju. To storimo zato, da odstranimo povečanje ali zmanjšanje vrednosti, ki naj ne bi bila posledica spin-off poteze temveč drugih dejavnikov. Dobljeno vrednost, iz katere je odstranjen ta splošni razvoj, poimenujemo intrinzična vrednost. V nalogi pridemo do pozitivnih rezultatov, ki so v skladu s podobnimi študijami. Z analizo prikazujemo, da vrednost oziroma tržna kapitalizacija po 180-ih dneh od zaključitve v povprečju zraste za 5.1 odstotek. Iz te vrednosti je že odštet splošen razvoj trga, ki se je v istem obdobju v povprečju povečal za 4 odstotke.
Ključne besede: spin-off, ustvarjanje vrednosti s poslovnimi potezami, intrinzična vrednost, kvantitativna analiza
Objavljeno v DKUM: 20.05.2015; Ogledov: 1302; Prenosov: 207
.pdf Celotno besedilo (872,40 KB)

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