Distinctive character of electronic and vibrational coherences in disordered molecular aggregates

Coherent dynamics of coupled molecules are effectively characterized by the two-dimensional (2D) electronic coherent spectroscopy. Depending on the coupling between electronic and vibrational states, oscillating signals of purely electronic, purely vibrational or mixed origin can be observed. Even in the "mixed" molecular systems two types of coherent beats having either electronic or vibrational character can be distinguished by analyzing oscillation Fourier maps, constructed from time-resolved 2D spectra. The amplitude of the beatings with the electronic character is heavily affected by the energetic disorder and consequently electronic coherences are quickly dephased. Beatings with the vibrational character depend weakly on the disorder, assuring their long-time survival. We show that detailed modeling of 2D spectroscopy signals of molecular aggregates providesdirect information on the origin of the coherent beatings.Comment: 7 pages, 4 figures, 1 tabl

Decoherence and Dephasing of Vibronic Excitons

In organic molecular assemblies, photo-induced energy and charge transfer is accompanied by significant intramolecular nuclear rearrangements. Therefore, optical excitations are described as quasiparticles excitons. Coupling to vibrational degrees of freedom is often a dominating factor in the description of the exciton dynamics, therefore the vibronic exciton theory has to be used. In this thesis, the significance of dephasing and decoherence of vibronic excitons in molecular systems is investigated and the signatures of electronic-vibrational interaction in the two-dimensional electronic spectra are analyzed with the focus on evolution of molecular excitation and quantum coherences. It is shown, that (i) quantum coherences of electronic, vibrational or mixed nature can be discriminated through the analysis of coherent oscillations in the two-dimensional spectrum, (ii) the effect of static energetic disorder on the coherences depends on the nature of the states involved in the quantum superposition, (iii) for vibronically-coupled systems, the lifetime of excitonic coherences are determined by the coupling to discrete modes of intramolecular vibrations and by proximity of the system parameters to an excitonic--vibrational resonance, (iv) the electronic and vibronic energy level structure of the six-porphyrin nanoring is determined by the non-trivial combined effect of energetic disorder, vibronic coupling and small geometric deformations of the nanoring

Experimental evidence that the invasive snail potamopyrgus antipodarum (Gray, 1843) survives passage through the digestive tract of common riverine fish

Potamopyrgus antipodarum is one of the most widespread invasive species worldwide and its expansion is ongoing. Although the snail has already been documented as surviving the digestive tract of various fish, there is insufficient data on potential riverine fish predators of P. antipodarum and of the ability of the snail to survive digestion by these fish. Lotic ecosystems are unfavourable for the upstream spread of this species by active movement and thus it is suspected that benthivorous riverine fish facilitate such upstream dispersion. In general, the results of this study indicated that P. antipodarum is not a preferable food object for the studied riverine fish. The study did indicate, however, that the invasive snail is capable of surviving the digestive tract of all the studied fish. As accidental consumption of abundant P. antipodarum with other food objects has already been documented, this study suggests that riverine fish can act as potential secondary dispersion vectors, facilitating the upstream dispersion of the snail

Būsite pats sau šeimininku

Vytauto Didžiojo universitetasŽemės ūkio akademij

Simple Gain-Scheduled Control System for Dissolved Oxygen Control in Bioreactors

An adaptive control system for the set-point control and disturbance rejection of biotechnological-process parameters is presented. The gain scheduling of PID (PI) controller parameters is based on only controller input/output signals and does not require additional measurement of process variables for controller-parameter adaptation. Realization of the proposed system does not depend on the instrumentation-level of the bioreactor and is, therefore, attractive for practical application. A simple gain-scheduling algorithm is developed, using tendency models of the controlled process. Dissolved oxygen concentration was controlled using the developed control system. The biotechnological process was simulated in fed-batch operating mode, under extreme operating conditions (the oxygen uptake-rate’s rapidly and widely varying, feeding and aeration rate disturbances). In the simulation experiments, the gain-scheduled controller demonstrated robust behavior and outperformed the compared conventional PI controller with fixed parameters

The research of air pollution in the environment of petroleum station

Vis didėjantis degalinių skaičius greta gyvenamųjų teritorijų kelią didelį nerimą dėl į aplinką išskiriamų cheminių teršalų. Degalinėse didžiausią taršą atmosferai sukelia lakiųjų organinių junginių garavimas, taip pat atvažiavusių į degalinę automobilių išmetamosios dujos. Visi šie teršalai gali sukelti neigiamą poveikį žmogaus sveikatai, įskaitant padidėjusią riziką susirgti vėžiu. Todėl siekiant, kad tarša neviršytų didžiausios leistinos normos, būtina vykdyti oro užterštumo stebėseną. Straipsnyje nagrinėjama degalinių skleidžiamos oro taršos problema. Pasirinktoje tipinėje miesto degalinėje dujų analizatoriumi Gasmet DX 4030 buvo atlikti aplinkos oro tyrimai aplink degalinę ir jos operatoriaus darbo vietose. Benzeno, azoto dioksido ir sieros dioksido neigiamas poveikis žmogui gali būti iki 100 m atstumu nuo degalinės, o degalinės operatoriaus darbo vietose dar padidėjusi ir formaldehido koncentracijaThe increasing number of petroleum stations near living areas causes a big worry because of their emissions. In any petroleum station the largest atmosphere pollution is caused by evaporation of volatile organic compounds and also vehicle exhaust. All the pollutants can make negative effect on human health including higher cancer risk. Therefore, a monitoring has to be held in order not to exceed the highest allowed norm of pollution. The article analyzes the problem of pollution caused by petroleum stations. Air samples were measured inside a typical town petroleum station as well as in the working place of an operator with a gas analyzer Gasmet DX 4030. Negative on human health concentration of gases benzene, nitrogen dioxide and sulfur dioxide was registered up to 100 m away from the petroleum station and also an increased concentration of formaldehyde was observed at the working place of the operator inside the stationVytauto Didžiojo universitetasŽemės ūkio akademij