МІСЦЕ СЕГМЕНТІВ «BUDGET» ТА «EKONOMY» У ГОТЕЛЬНОМУ БІЗНЕСІ УКРАЇНИ. (ROLE OF SEGMENTS «BUDGET» AND «EKONOMY» IN THE UKRAINE HOTEL BUSINESS.)

Проаналізовано недоліки в готельному обслуговуванні туристів після проведення чемпіонату з футболу «Євро-2012», встановлено залежність туристичної привабливості України від цінової політики підприємств готельного бізнесу. (Shortcomings in hotel service of tourists on realization of football championship «Euro 2012 « were analysed, the dependence of tourist attractiveness of Ukraine on price politics of hotel business enterprises was determined.

Optical transmittance of carbon suspensions in polymer matrixes under powerful pulsed laser irradiation

The effect of optical limiting is investigated in the suspensions of carbon microparticles in aqueous gelatin gel and epoxy resin. Both transient and permanent changes of optical transmittance are observed after the irradiation by a Q-switched YAG:Nd³⁺ laser pulses. The experimental results are explained with taking into account the formation of micro-bubbles filled with water steam and with gaseous products of decomposition of the matrix. In the epoxy resin suspensions, the laser-induced permanent changes of transmittance are caused by pyrolysis of epoxy oligomers in the vicinity of laser-heated carbon particles

Revisiting physical distancing threshold in indoor environment using infection-risk-based modeling

Physical distancing has been an important policy to mitigate the spread of the novel coronavirus disease 2019 (COVID-19) in public settings. However, the current 1-2m physical distancing rule is based on the physics of droplet transport and could not directly translate into infection risk. We therefore revisit the 2-m physical distancing rule by developing an infection-risk-based model for human speaking. The key modeling framework components include viral load, droplets dispersion and evaporation, deposition efficiency, viral dose-response rate and infection risk. The results suggest that the one-size-fits-all 2-m physical distancing rule derived from the pure droplet-physics-based model is not applicable under some realistic indoor settings, and may rather increase transmission probability of diseases. Especially, in thermally stratified environments, the infection risk could exhibit multiple peaks for a long distance beyond 2 meters. With Sobol’s sensitivity analysis, most variance of the risk is found to be significantly attributable to the variability in temperature gradient, exposure time and breathing height difference. Our study suggests there is no such magic 2m physical distancing rule for all environments, but it needs to be used alongside other strategies, such as using face cover, reducing exposure time, and controlling the thermal stratification of indoor environment

A Map of Dielectric Heterogeneity in a Membrane Protein: the Hetero-Oligomeric Cytochrome b 6 f Complex

The cytochrome b6f complex, a member of the cytochrome bc family that mediates energy transduction in photosynthetic and respiratory membranes, is a hetero-oligomeric complex that utilizes two pairs of b-hemes in a symmetric dimer to accomplish trans-membrane electron transfer, quinone oxidation–reduction, and generation of a proton electrochemical potential. Analysis of electron storage in this pathway, utilizing simultaneous measurement of heme reduction, and of circular dichroism (CD) spectra, to assay heme–heme interactions, implies a heterogeneous distribution of the dielectric constants that mediate electrostatic interactions between the four hemes in the complex. Crystallographic information was used to determine the identity of the interacting hemes. The Soret band CD signal is dominated by excitonic interaction between the intramonomer b-hemes, bn and bp, on the electrochemically negative and positive sides of the complex. Kinetic data imply that the most probable pathway for transfer of the two electrons needed for quinone oxidation–reduction utilizes this intramonomer heme pair, contradicting the expectation based on heme redox potentials and thermodynamics, that the two higher potential hemes bn on different monomers would be preferentially reduced. Energetically preferred intramonomer electron storage of electrons on the intramonomer b-hemes is found to require heterogeneity of interheme dielectric constants. Relative to the medium separating the two higher potential hemes bn, a relatively large dielectric constant must exist between the intramonomer b-hemes, allowing a smaller electrostatic repulsion between the reduced hemes. Heterogeneity of dielectric constants is an additional structure–function parameter of membrane protein complexes

Toward Time-Resolved Circular Dichroism Spectroscopy of Photosynthetic Proteins: Accessing Excitonic States

The focus of this thesis is the study the physical properties and functions of photosynthetic proteins and biomimetic artificial systems that are responsible for electron and energy transfer, and could facilitate the development of biomimetic, renewable energy sources. In particular, transient absorption and circular dichroism spectroscopy, and structure based quantum mechanical simulations have been used to determine triplet state energy transfer in the Fenna-Matthews-Olson antenna protein complex and the effective dielectric constant deep within cytochrome b6f and bc1 proteins complexes. ^ The Fenna-Matthews-Olson protein complex was one of the first proteins crystallized. Since then, a substantial study of its properties has been conducted. The protein became a model system for a lot of theoretical and experimental work because of strongly bound pigments that form the excitonic states, which play a major role in efficient energy transfer, photo-protection, charge separation and electron transfer. However, it is often difficult or even impossible to access those pigments with conventional spectroscopic tools. ^ In this work, I implemented novel time-resolved circular dichroism spectroscopic tools in nanosecond and femtosecond time domains. The first time-resolved circular dichroism spectra have been obtained and provide very rich and unique information even at room temperature. The measured transient circular dichroism spectra have uniquely identified the previously observed 11 microsecond component and assigned it to a new transition. ^ The low-temperature absorbance and circular dichroism spectroscopy coupled with structure-based excitonic simulation have been applied to study new Fenna-Matthews-Olson mutants that reveal incredible details about the excitonic energy landscape of the FMO protein. ^ The proof-of-concept femtosecond transient circular dichroism spectrometer has been built, and the first round of experiments using it appear promising. ^ This novel circular dichroism tools will be used to study photosynthetic proteins such as Fenna-Matthews-Olson antenna protein complex and Photosystem I intrinsic charge separation via direct probing and(or) excitation of strongly coupled pigments.

Predictive First-principles Modeling of a Photosynthetic Antenna Protein : The Fenna-Matthews-Olson Complex

High efficiency of light harvesting in photosynthetic pigment-protein complexes is governed by evolutionary-perfected protein-assisted tuning of individual pigment properties and inter-pigment interactions. Due to the large number of spectrally overlapping pigments in a typical photosynthetic complex, experimental methods often fail to unambiguously identify individual chromophore properties. Here we report a first principles-based modeling protocol capable of predicting properties of pigments in protein environment to a high precision. The technique was applied to successfully uncover electronic properties of the Fenna-Matthews-Olson (FMO) pigment-protein complex. Each of the three subunits of the FMO complex contains eight strongly coupled bacteriochlorophyll a (BChl a) pigments. The excitonic structure of FMO can be described by an electronic Hamiltonian containing excitation (site) energies of BChl a pigments and electronic couplings between them. Several such Hamiltonians have been developed in the past based on the information from various spectroscopic measurements of FMO; however, fine details of the excitonic structure and energy transfer in FMO, especially assignments of short-lived high-energy sites, remain elusive. Utilizing polarizable embedding QM/MM with the effective fragment potentials (EFP) we were able to compute the electronic Hamiltonian of FMO that is in general agreement with previously reported empirical Hamiltonians and quantitatively reproduces experimental absorption and circular dichroism (CD) spectra of the FMO protein. The developed computational protocol is sufficiently simple and can be utilized for predictive modeling of other wild type and mutated photosynthetic pigment-protein complexes.peerReviewe

Pathways of transmembrane electron transfer in cytochrome bc complexes : dielectric heterogeneity and interheme Coulombic interactions

The intramembrane cytochrome <i>bc</i>₁ complex of the photosynthetic bacterium Rhodobacter capsulatus and the cytochrome <i>b</i>₆<i>f</i> complex, which functions in oxygenic photosynthesis, utilize two pairs of <i>b</i>-hemes in a symmetric dimer to accomplish proton-coupled electron transfer. The transmembrane electron transfer pathway in each complex was identified through the novel use of heme Soret band excitonic circular dichroism (CD) spectra, for which the responsible heme–heme interactions were determined from crystal structures. Kinetics of heme reduction and CD amplitude change were measured simultaneously. For <i>bc</i>₁, in which the redox potentials of the transmembrane heme pair are separated by 160 mV, heme reduction occurs preferentially to the higher-potential intermonomer heme pair on the electronegative (n) side of the complex. This contrasts with the <i>b</i>₆<i>f</i> complex, where the redox potential difference between transmembrane intramonomer p- and n-side hemes is substantially smaller and the n–p pair is preferentially reduced. Limits on the dielectric constant between intramonomer hemes were calculated from the interheme distance and the redox potential difference, Δ<i>E</i>_m. The difference in preferred reduction pathway is a consequence of the larger Δ<i>E</i>_m between n- and p-side hemes in <i>bc</i>₁, which favors the reduction of n-side hemes and cannot be offset by decreased repulsive Coulombic interactions between intramonomer hemes