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To understand the influence of interchromophoric arrangements on photo-induced processes and optical properties of aggregates, it is fundamental to assess the contribution of local excitations [charge transfer (CT) and Frenkel (FE)] to exciton states. Here, we apply a general procedure to analyze the adiabatic exciton states derived from time-dependent density functional theory calculations, in terms of diabatic states chosen to coincide with local excitations within a restricted orbital space. In parallel, motivated by the need of cost-effective approaches to afford the study of larger aggregates, we propose to build a model Hamiltonian based on calculations carried out on dimers composing the aggregate. Both approaches are applied to study excitation energy profiles and CT character modulation induced by interchromophore rearrangements in perylene bisimide aggregates up to a tetramer. The dimer-based approach closely reproduces the results of full-aggregate calculations, and an analysis in terms of symmetry-adapted diabatic states discloses the effects of CT/FE interactions on the interchange of the H-/J-character for small longitudinal shifts of the chromophores.

We theoretically analyse the equation of topological solitons in a chain of particles interacting via a repulsive power-law potential and confined by a periodic lattice. Starting from the discrete model, we perform a gradient expansion and obtain the kink equation in the continuum limit for a power law exponent $n \ge 1$. The power-law interaction modifies the sine-Gordon equation, giving rise to a rescaling of the coefficient multiplying the second derivative (the kink width) and to an additional integral term. We argue that the integral term does not affect the local properties of the kink, but it governs the behaviour at the asymptotics. The kink behaviour at the center is dominated by a sine-Gordon equation and its width tends to increase with the power law exponent. When the interaction is the Coulomb repulsion, in particular, the kink width depends logarithmically on the chain size. We define an appropriate thermodynamic limit and compare our results with existing studies performed for infinite chains. Our formalism allows one to systematically take into account the finite-size effects and also slowly varying external potentials, such as for instance the curvature in an ion trap., Comment: 7 pages, 3 figures; typos corrected; abstract replaced with the one of the published version; version published in the special issue "Many Body Quantum Chaos" of Condensed Matter, in memory of Professor Shmuel Fishman

In organic materials, coupling of electronic excitations to vibrational degrees of freedom results in polaronic excited states. Through numerical calculations, we demonstrate that the vibrational distortion field accompanying such a polaron scales as the product of the excitonic interaction field and the exciton coherence function. This scaling relation is derived analytically in the regime where excitonic interactions are weak, yet it is shown to remain valid for interaction strengths ranging up to physically relevant values. Moreover, it is not affected by the magnitude of exciton-vibrational coupling or the presence of disorder in the molecular transition energies, despite the dramatic changes observed in the excited state. An application to helical MOPV4 aggregates is presented, followed by a quantitative study of the vibrational distortion field when excitonic interactions are strong. Our findings allow for a straightforward interpretation of widely varying polaron profiles, thereby facilitating the characterization of organic excited states.

Pasibaigus Nepriklausomybės kovoms, Lietuvos kariuomenėje buvo ypač jaučiamas ginkluotės poreikis. Šių išteklių paruošimas galimiems karo veiksmams, skirtingai nuo kito karinio turto, buvo pirmaeilis dalykas. Bandyta savo jėgomis gaminti reikalingus karinius reikmenis. Kadangi iš carinės Rusijos nepaveldėta jokios karinės pramonės infrastruktūros, teko nuo pamatų kurti visiškai naują ir žemės ūkio kraštui nežinomą karo pramonės šaką. 1921 m. pasitaikius galimybei Lietuvoje įsteigti šaudmenų gamybos fabriką, karinė vadovybė ėmėsi aktyviai įgyvendinti šią idėją. Iš Vokietijoje likviduojamų karo pramonės įmonių užsakyta šovinių gamybos techninė įranga, tačiau jai saugoti pirmiau reikėjo rasti tinkamas patalpas. Tokios reikšmės objektui buvo keliami išskirtiniai reikalavimai, tačiau dėl ribotų valstybės finansų tikėtasi pritaikyti jau esamus šalyje pastatus. Straipsnyje nagrinėjama, kaip vyko pasiruošimas amunicijos fabriko įkūrimui. Lietuvos centriniame valstybės archyve rasti dokumentai atskleidžia iki šiol nežinomų detalių apie bandymą Šiauliuose įsteigti pirmąjį šovinių gamybos fabriką. When the struggles for Lithuania’s independence were over, the Lithuanian armed forces needed arms. Task number one was to provide the army with military supplies so it was decided to start producing military goods in the country. Tsarist Russia left neither military infrastructure nor military industry there so the rural country had to create them on its own. In 1921 Lithuania had a chance to start producing armaments, and the initiative was supported by military authorities. All necessary technology and equipment were ordered from liquidated armaments manufacturers in Germany but firstly suitable premises had to be found. Although there were special requirements for the object of such importance but the State lacked funds so it was decided to use available premises. Preparations to start producing armaments in Šiauliai are being analyzed in the paper. Some material kept in the Lithuanian Central State Archives have revealed unknown details of the issue.

In dieser Arbeit werden Untersuchungen an selbstorganisierten, tubulären J-Aggregaten amphiphiler Cyaninfarbstoffe, 3,3’-bis(2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’-dioctylbenzimidacarbocyanine, im Weiteren C8S3 genannt, dargestellt. Ziel der Arbeit ist es an die Aggregate eine Lage Polyelektrolyte zu adsorbieren, sowie nachzuweisen, dass diese Methode geeignet ist, um einen Energietransfers zwischen dem Aggregat und funktionellen Gruppen in der Adsorbatschicht zu erreichen. Die tubulären Aggregate sind supramolekulare Strukturen, die sich spontan und selbstorganisiert aufgrund des amphiphilen Charakters der Cyaninfarbstoffe in wässrigen Lösungen bilden. Die Farbstoffe ordnen sich in einer Doppelschicht an, die die Wand der Röhren bildet mit etwa 13 nm Durchmesser und Längen bis zu 1 µm und mehr. Die Aggregate bilden exzitonische Anregungen aus, die sich in einer typischen Rotverschiebung (J-Aggregat) der optischen Absorption sowie einer charakteristischen Aufspaltung in mehrere schmale Banden zeigt. Die negative Oberflächenladung der Aggregate wird genutzt, um positiv geladene Polyelektrolyte (PE) anzulagern. Drei exemplarische PE, die sich in Ladungsdichte und Persistenzlänge unterscheiden, werden untersucht. In allen drei Fällen ist es gelungen Aggregate mit einer 2-3 nm dicken Polyelektrolytschicht zu umhüllen, wobei die molekulare Ordnung der Aggregate nur geringfügig gestört wird. Durch Einsatz von Farbstoffdotierten Polyelektrolyten konnten Experimente zum Nachweis des Förster-Energietransfer durchgeführt werden. Die Farbstoffdotierungen sind kovalent an die PE gebunden, wodurch sie in der PE-Umhüllung lokalisiert sind. Durch Wahl geeigneter Farbstoffe konnte ein Energietransfer vom Farbstoff (Donator) zum Aggregat als auch umgekehrt vom Aggregat zum Farbstoff (Akzeptor) nachgewiesen werden. Es ergeben sich hohe Transferraten, da die Farbstoffe in der PE-Schicht deutlich dichter am Aggregat liegen, als die theoretisch berechneten Förster-Radien. The following dissertation deals with investigation on tubular J-aggregates of amphiphile cyanine-dyes, 3,3’-bis(2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’-dioctylbenzimidacarbocyanine (C8S3). Aim of this work is to adsorb a layer of polyelectrolyte on C8S3-aggregates and to proof the capability of this method to establish an energy-transfer between the aggregate and functional groups in the adsorbate-layer. The tubular aggregates are supramolecular structures, that form entirely spontaneous and self-organized due to amphiphilic character of the investigated cyanine-dye derivative in aqueous solution. These dyes arrange themselves in a double-layer, assembling the hull of the tubular structure, with outer tube-diameters of approximately 13 nm and length of more than 1 µm. Due to the regular and dense arrangement of the dyes excitonic excitation establishs with the structure, that causes a J-aggregate typical red-shift in absorption and a characteristic band-splitting. The aggregates offer a negative surface-charge in aqueous solution. This is utilized to adsorb oppositely charged polyelectrolytes (PE) by electrostatic adsorption. It is shown exemplarily for three different kinds of PE that differ in charge-density and persistence-length. In all three cases a successful PE-wrapping of 2-3 nm thickness has been performed. The molecular order within the aggregates has been disturbed only weakly. Dye-labelled PE experiments proof Förster-energytransfer. The dye-labels are covalently bound to PE, fixing and localizing the labels in the wrapping-layer. With appropriate dye-labels an energy-transfer from labels in the coating (donor) towards the aggregate and vice versa, from aggregate to the dye-labels (acceptor) has been revealed. Caused by the localisation of the labels within the PE-coating, the distances of aggregate and label are always smaller than the theoretically calculated Förster-radii, resulting in a high efficiency of the transfer-rates.

The members of the Lithuanian minority in Poland followed attentively and supported the changes in Lithuania initiated by Sąjūdis (the Reform Movement of Lithuania). When Lithuania declared its independence on March 11, 1990, Polish Lithuanians repeatedly appealed to Polish authorities to recognize its independence and the constituted government. The Soviet Union imposed an economic blockade on Lithuania; therefore Polish Lithuanians organized the Anti-blockade Fund of Lithuania. They collected and transported relief aid to Lithuania. After the tragic events of January 13, 1991, Polish Lithuanians organized the medical help and supported Lithuanian refugees in Poland. They managed to get the radio transmitter to transmit radio programmes to Lithuania. In order to support the independent country, Polish Lithuanians organized protest rallies against the Soviet activities in Lithuania in Punskas and in Warsaw.

We report on novel InGaN/GaN quantum well/polyfluorene heterostructures where efficient Förster energy transfer from the well to the organic layer occurs. We show that Mott-Wannier excitons dominate the quantum well luminescence in the quantum wells in the 77 to at least 225 K range and are responsible for the efficient energy channeling to the polyfluorene films. © 2007 American Institute of Physics. 893 355 356 Sponsors: Austrian Research Centers (ARCS) Infineon Austrian Fed. Minist. Educ., Sci. Cult. (BMBMWK) FFG Austrian Nano Initiative Cited By :1

Selective Laser Sintering (SLS) and Selective Laser Melting (SLM) are parent Additive Manufacturing processes using a laser to solidify metallic, ceramic, polymer or composite powders. During the process, the object is built layer by layer. A laser source is responsible for the consolidation, by local heating. The light is deviated by a scanning head according to the instructions of an STL file. Then partial fusion of the particles takes place, followed by a solidification of the liquid created. Kinetics of these steps are very high and play an important role in the final microstructure (rearrangement of the particles, pore creation, residual stresses). In the case of polymers and composites the technique is now well understood and widely used, but for metals and ceramics it suffers from a lack of precision, surface roughness and poor mechanical properties. The goal of this Ph.D. work is to understand the effect of the thermal gradients on the consolidation process, using different laser parameters (power, pulse frequency, scan speed,…). In SLS, microscopic thermal gradients arise, due to the fact that the laser is pulsed and that only the exterior of the powder particles is molten. A thermal model to describe the interaction between a laser beam and a (spherical) grain is proposed. This model allows for the incorporation of the latent heat of fusion and for a realistic surrounding. The absorbed laser intensity is modeled by means of the Mie theory. Experiments where two particles of powder are isolated and illuminated by the laser are carried out in order to measure the interparticular necks and the volume of liquid formed for different repetition rates. The thermal model leads to good predictions of the particles final sintering state. Fluid flow models are investigated in order to determine the dynamic of the molten liquid. The main issue is to explain the capillary flow mechanisms leading from the molten material to the neck formation. Two models are derived to simulate the fluid flow between the particles. The first one simulates a capillary flow between two parallel plates. The second one deals with energetic considerations arising from Frenkel's principle. In both cases, the final output is the liquid life-time necessary to get the interparticular neck lengths experimentally observed. We point out that the two models predict the same liquid lifetime, although they are derived with different hypotheses. In SLM, continuous lasers are used and one has to deal with macroscopic thermal gradients, since the particles are completely molten. A very high laser power is used and the negative thermal effects (like thermal stresses or balling effects) are important. A solution to control them is to adjust the scanning strategy. Four scanning strategies are investigated for material with different thermal conductivities. The three-dimensional model used to describe the laser-matter interactions and the temperature evolution of the scanned powder bed allows for a finite latent heat (Stefan-problem) and for conductivity modifications due to the consolidation. We show that this finite element thermal model can be efficiently used to anticipate most of the problems (like cracks or balling) arising in practice. The benefit of avoiding thermal gradients is shown, in particular by EBSD analysis. Finally, applications of the SLS/SLM technique on different pieces built during this work are shown. A new way to build support structure is also proposed.