In situ mapping of the energy flow through the entire photosynthetic apparatus

Absorption of sunlight is the first step in photosynthesis, which provides energy for the vast majority of organisms on Earth. The primary processes of photosynthesis have been studied extensively in isolated light-harvesting complexes and reaction centres, however, to understand fully the way in which organisms capture light it is crucial to also reveal the functional relationships between the individual complexes. Here we report the use of two-dimensional electronic spectroscopy to track directly the excitation-energy flow through the entire photosynthetic system of green sulfur bacteria. We unravel the functional organization of individual complexes in the photosynthetic unit and show that, whereas energy is transferred within subunits on a timescale of subpicoseconds to a few picoseconds, across the complexes the energy flows at a timescale of tens of picoseconds. Thus, we demonstrate that the bottleneck of energy transfer is between the constituents

Transfer of Vibrational Coherence Through Incoherent Energy Transfer Process in F\"{o}rster Limi

We study transfer of coherent nuclear oscillations between an excitation energy donor and an acceptor in a simple dimeric electronic system coupled to an unstructured thermodynamic bath and some pronounced vibrational intramolecular mode. Our focus is on the non-linear optical response of such a system, i.e. we study both excited state energy transfer and the compensation of the so-called ground state bleach signal. The response function formalism enables us to investigate a heterodimer with monomers coupled strongly to the bath and by a weak resonance coupling to each other (F\"{o}rster rate limit). Our work is motivated by recent observation of various vibrational signatures in 2D coherent spectra of energy transferring systems including large structures with a fast energy diffusion. We find that the vibrational coherence can be transferred from donor to acceptor molecules provided the transfer rate is sufficiently fast. The ground state bleach signal of the acceptor molecules does not show any oscillatory signatures, and oscillations in ground state bleaching signal of the donor prevail with the amplitude which is not decreasing with the relaxation rate.Comment: 11 pages, 9 figure

European Solidarity Corps Projects Responding to COVID-19: Implications for Future Crises

In 2020, the COVID-19 pandemic hit the world in an unprecedented way, affecting various areas of the economy and society, including nonprofits and volunteering. However, nonprofits and volunteering did not just face challenges due to the pandemic; they also played a role in dealing with it. This article focuses on the European Solidarity Corps (ESC), an EU initiative that promotes solidarity through volunteering in countries worldwide. There was a content analysis of all the ESC projects with pandemic-relevant keywords. Though the ESC requests for proposals in the first year of the pandemic did not address the pandemic, about 8% of projects explicitly named the pandemic as either a main or secondary reason for the projects. The ESC projects represent a way to relatively flexibly allocate public funding for local and international volunteer projects dealing with various humanitarian crises, such as COVID-19 or the war in Ukraine

Risk Management in Service Sector: Establishing of a Small Cafe

Tato diplomová práce se zabývá podnikatelským plánem na založení malé kavárny. Na základě vypracování kritické analýzy rizik, marketingového výzkumu, analýzy trhu a analýzy trhu pomocí dotazníku má tato práce za úkol navrhnout konkrétní plán, dle které by mělo být možné založit malou kavárnu a díky tomu získat hodnotu pro investora.This master thesis is concerned with the business plan of establishing a small cafe. Based on the critical analysis of the risks, marketing research, market analysis and survey solutions, this thesis is aiming to suggest a specific plan according to which it would be possible to establish the small cafe and get a monetary value for the investor as a consequence.

Operational Degradation of Engine Oil in Agricultural Technology

Proposed paper is focused on description and observation of operational degradation of engine oil in agricultural technology. Engine oil is one of the most important liquids used in combustion engines. Correct function of any machine is based on the appropriate selection of lubricants; moreover, it is also important to care for the entire lubrication system. Determining the condition of the oil used in operational conditions is very important for potential further oil use. Previously, engine oil had to be changed after expiration of legally valid intervals regardless of its actual performance parameters. However, its usage may be extended if engine oil parameters meet the legal requirements. This can be achieved by removing engine oil samples from machines on a regular basis. By examining the samples taken, it is possible to determine the actual oil state. In such manner, it is possible to prolong interchange periods and save both the financial resources and environment.O

Analysis of surface defects in composites using digital image correlation and acoustic emission

This work employs the acoustic emission (AE) method for material state monitoring. AE presents a non-destructive evaluation technique, which could be used for detection of microstructural changes in composite material. Work describes the process of acquisition of AE in tensile loading of carbon composite materials. In course of tensile stress, the composite was monitored with optical method, applying principles of digital image correction (DIC). Optical stereovision method enables calculation of field shift and field of proportional deformation at composite surface. The objective is analysis of damage in carbon composite materials and employ the methodology of AE signal processing for facilitation of early damage diagnostics and prediction of structural failure. For this purpose, the experimental setup was designed to obtain results from 50 nominally identical composite samples in tensile loading test. Force load applied on samples was synchronically recorded along with AE and image data. Experimental data were subsequently analysed in a way enabling the description of typical phenomena in course of every measurement. Results show that observation of AE sources could be employed in facilitation of early damage diagnostics and establishment of failure prognosis. It is about internal changes in composite material.O

Mapping of exciton-exciton annihilation in a molecular dimer via fifth-order femtosecond two-dimensional spectroscopy

We present a theoretical study on exciton–exciton annihilation (EEA) in a molecular dimer. This process is monitored using a fifth-order coherent two-dimensional (2D) spectroscopy as was recently proposed by Dostál et al. [Nat. Commun. 9, 2466 (2018)]. Using an electronic three-level system for each monomer, we analyze the different paths which contribute to the 2D spectrum. The spectrum is determined by two entangled relaxation processes, namely, the EEA and the direct relaxation of higher lying excited states. It is shown that the change of the spectrum as a function of a pulse delay can be linked directly to the presence of the EEA process

Academic Achievement, School Absence and Self-Concept in Czech Prepubescent Children with Overweight and Obesity

Problem. The paper offers findings about selected educational aspects of children’s academic performance, examined here in terms of sociodemographic variables, BMI percentile values, cognitive test scores, weight bias internalization scale and self­ ­concept scale with an aim to detect whether and to what extent these factors contribute to children’s school results. Methods. 557 fifth graders were administered Vana’s Intelligence Test, the Piers‑Harris 2 self­‑concept questionnaire and other tools. Children’s educational aspects were assessed in terms of school Absence, Grade Point Average, and Czech and Mathematics grades, with data obtained from their most recent report cards under the Informed consent of their legal representatives and in compliance with ethical standards. Results. Prepubescent children from stronger socio­‑economic backgrounds suffer from overweight/obesity less often and perform slightly better at school. The present results suggest a link between weight bias internalization and overweight/obesity, and a somewhat weaker link between self­‑concept and overweight/obesity in the non­‑clinical population of prepubescent children. In these relationships of overweight/obese children, as in the cases of alarmingly high school absence, gender is an important variable. Multinomial logistic regression modelling the relationship between Czech and Mathematics grades and selected factors discovered that chances for a worse grade were significantly reduced by the results of Vana’s Intelligence Test in both the subjects, while the Self‑concept total score proved to be an insignificant factor. Conversely, pupils’ Czech grades were negatively influenced by increased BMI (quartile), higher Absence rate, male Gender, Presence of only one parent in the family and WBI, while in Mathematics, in addition to the above­ ­discussed, significant regressors only included Absence and Presence of only one parent. Discussions. The results of the Self‑concept total score, the level of which is generally lower in girls than in boys in the population of Czech prepubescent children, agree with other authors’ experience. The connection between the male sex and poorer performance in Czech can be partly explained by the fact that the development of speech, reading, writing and grammar is generally less complicated for school­‑age girls than boys. We can ask why a higher BMI quartile increases the chances of a worse grade only in the case of Czech language? So far, we can only speculate about the causes. In our opinion, it is possible that the impact of parents’ education on the performance of children of this age is more pronounced in the Czech language (compared to Mathematics). The other possibility of the impact of the BMI quartile on the Czech grade is the significant predominance of boys in the o/o group. On the other hand, it should be noted that this argument would not explain the o/o children’s poorer Grade Point Average score. However, we believe that the above reasons answer partially this question. Conclusion. The vulnerability of o/o girls is pronounced in some domains of Selfconcept and Weight bias internalization, while in boys it is reflected in the more frequent occurrence of high levels of Absenteeism, with the precise causes of this being still subject to speculation. In this regard, workers in the cooperating professions should pay continuous attention to strengthening the desirable aspects of education and healthy lifestyle among vulnerable groups of children. Educational aspects of overweight/obese children should therefore continue to receive increased attention

Adaptive predictive control of laboratory heat exchanger

Heat exchange belongs to the class of basic thermal processes which occur in a range of industrial technologies, particularly in the energetic, chemical, polymer and rubber industry. The process of heat exchange is often implemented by through-flow heat exchangers. It is apparent that for an exact theoretical description of dynamics of heat exchange processes it is necessary to use partial differential equations. Heat exchange is namely a process with distributed parameters. It is also necessary to take into account its nonlinear and stochastic character. In spite of these facts, most of thermal equipment is controlled by digital modifications of PID controllers at present. This paper deals with identification of a dynamic behaviour of a through-flow heat exchanger and a design of a self-tuning predictive controller for its control. The designed controller was verified by a real-time control of an experimental laboratory heat exchanger

Desorption/ablation of lithium fluoride induced by extreme ultraviolet laser radiation

The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoride targets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR) or extreme ultraviolet (XUV) lasers for the pulsed ablation and thin film deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoride targets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation) of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code) taking into account laser heating and surface evaporation of the lithium fluoride target occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave) model.Web of Science61213813