Search

Anthropogenic pollution of marine ecosystems is one of the main sources of polycyclic aromatic hydrocarbons (PAHs). Marine bivalves are often used as bioindicators of environmental pollution due to their wide distribution and capability of xenobiotic bioaccumulation. The aim of the present study was to assess the presence of PAHs in soft tissues of wedge clams Donax trunculus (Linnaeus, 1758), collected from sublittoral sandy habitats at different locations off the Bulgarian Black Sea coast. Wedge clams from the different locations showed variations in the content of accumulated PAHs’ compounds. The concentrations of PAHs were measured by gas chromatography system with mass spectrometry detection. The total PAHs content (sum of 13 PAHs’ compounds) measured was in the range from 5.59 to 50.50 ng/g wet weight and was comparable with other European studies. The compounds phenanthrene and fluorene were most abundant in all analyzed samples. The results showed that low molecular weight (LMW) PAHs (2 and 3 aromatic rings) were predominant, accounting for 91% of the total PAHs levels, while high molecular weight (HMW) PAHs (4–5- and 6- rings) presence was 8.9% on average. The ratio LMW/HMWPAHs was higher than one, suggesting predominant pollution of petrogenic origin. The concentrations of benzo (a)pyrene did not exceed the limit set in EC Regulation although it was detected in 20% of the analyzed samples. In conclusion, maximum overall PAHs content was found in clams from Arkutino, while minimum PAHs content was present in samples from Elenite. The Sum PAH4 (sum of four polycyclic aromatic hydrocarbons: benzo[a]pyrene, chrisene, benzo[a]anthracene, and benzo[b]fluoranthene) in the wedge clams for all localities studied was below legislation limits. Data from the present research can be used for assessing pollution levels in the marine environment and also risk of human exposure to PAHs using D. trunculus as bioindicator species.

Plastic pollution in seawaters is ubiquitous, but quantitative estimates on the floating microplastics in the Black Sea are still limited. Plastics may adsorb persistent environmental contaminants, thus representing a potential risk for marine organisms. Aim: Thе aim of the study was evaluation of the presence and characteristics of microplastic particles (MPs) in waters from the Black Sea coast of Bulgaria. Materials and methods: Samples of coastal waters were collected from March 2021 to April 2022 from different stations on the Black Sea coast, including protected, aquaculture and industrial areas. In order to determine the number of plastic particles, 23 samples were collected from the surface waters at depth of 1–3 m close to the Bulgarian shore. Samples were treated with H2O2, plastic particles were isolated by density separation and filtered over a membrane filter. Identification analysis of micro particles (< 5 mm) was performed visually by microscopy. Main results: Results indicated widespread presence of microplastics in coastal waters. Mean MPs concentration was calculated 7.3 ± 4.9 pt/l. The comparison of the North, Varna and South sampling area showed that there is no significant difference in the abundance of plastic particles. The most dominant type forms were fibres followed by fragments. The most abundant size class of fragments was 101–500 μm Ferret diameter. Conclusion: Further studies are needed in order to fill knowledge gap and to evaluate distribution of plastic particles in the Black Sea and their potential ecological risk.

In skeletal muscles, the sialic acids have a great significance for their functional maintenance and proper structural organization. Our work described the expressions of St3gal, St6gal and St6galnac sialyltransferases specific for glycoproteins in mouse skeletal muscles and murine C2C12 myotubes. Lectin histochemistry, cytochemistry and lectin blot were used to demonstrate the membrane localization and the electrophoretic profiles of α-2,3- and α-2,6-sialylated glycoproteins. The expression levels of sialyltransferases were analysed by real time RT-PCR and western blot. The enzymes St6gal2 and St6galnac1 were not expressed in skeletal muscle tissue and C2C12 myotubes. In both experimental groups, mRNAs of the St3gal family prevailed over the mRNA expressions of the St6gal and St6galnac families. The profiles of sialyltransferase expressions showed differences between the two experimental groups, illustrated by the absence of expressions of the mRNA for the St3gal6 and St6galnac3 genes in the C2C12 cell samples and by the different shares of the enzymes St3gal3 and St3gal4 in both experimental groups. The different patterns of enzyme expressions in both experimental groups corresponded with differences between their α-2,3- and α-2,6-sialylated glycoprotein profiles. These results could be a useful addendum to the knowledge concerning the glycosylation of the skeletal muscle tissue.

Solar gravitational multipolar moments have not been yet extensively analysed. However, they are at the crossroads of solar physics, solar astrometry, celestial mechanics, and General Relativity. Their values reflect the physics of solar models: non-rigid rotation, solar latitudinal rotation, solar-core properties, solar-cycle variations, and structure evolution. Their temporal variations are still often neglected; they are yet an essential aspect for constraining solar-cycle modelling or solar-evolution theories. They induced planet-planet inclinations in multi-transiting systems gravitating in the neighbouring of a star, leading to key issues future studies. This paper is devoted to an analytical analysis; a second part will address a helioseismology analysis.

Marine biotoxins are produced by certain phytoplankton species and used to accumulate in filter-feeding marine organisms. The occurrence of marine biotoxins in all aquatic environments and latitudes is variable in time and space. Thus, it is an essentially natural phenomenon, but the occurrence of toxigenic phytoplankton cannot be completely avoided or eliminated. A serious concern appears if these substances accumulate at high levels in seafood. If it is consumed by mammals including humans, severe illness of consumers of intoxicated seafood may result. The aim of this study is to assess the presence of marine biotoxins in plankton samples taken in 2021 and to compare the determined levels with a previous period. Plankton samples (n = 21) were collected in 2021 along the whole Bulgarian coastline (Black Sea). The presence of hydrophilic (domoic acid (DA)) and lipophilic toxins (okadaic acid, dinophysis toxin – 1, dinophysis toxin -2, azaspiracid-1, goniodomin A, pectenotoxin-2 (PTX2), yessotoxin, spirolide-1 and gymnodimine A) was investigated via liquid chromatography – tandem mass spectrometry (LC-MS/MS). Results indicated the presence of only DA in three samples and PTX2 in two samples. The positive samples were sporadically distributed throughout the study period. During 2016–2019, LC-MS/MS analysis confirmed the presence of DA, PTX2, YTX, SPX-1 and GDA in plankton net samples collected from the same locations reported here. The matching toxins (DA and PTX2) were at comparable levels in both periods of investigation, thus lower than in other European waters where harmful algal blooms are registered. These results show the persistent appearance of some marine biotoxins in Bulgarian waters. Although levels were low in the monitored periods, a constant monitoring is required in order that toxic events by seafood consumption be avoided.

The program and results of physical research in the international (5 countries) space experiment «The situation (1 stage)», conducted onboard the Russian segment of the International Space Station (ISS) in the period 27.02.2013 to 09.05.2015, is presented. The methods and scientific tasks of the experiment and the composition of the Plasma-wave complex based on the combined wave diagnostics method are described in detail, and designed to conduct geophysical studies through long-term monitoring measurements of the electromagnetic parameters of the ionosphere plasma and plasma-wave processes associated with the manifestation in the ionosphere of the solar-magnetosphere-ionosphere and ionosphere-atmosphere relationships, i. e., parameters of space weather. Studies in the near-surface zone of plasma-wave processes of interaction of an extra-large spacecraft, like ISS, with the ionosphere are necessary for both applied and fundamental geophysical studies. The electric and magnetic fields and currents measured at the surface of the ISS are determined by the parameters of the surrounding ionosphere plasma and the nature of the interaction of the materials on the surface with this medium. Key words: orbital space station, fundamental space research, ionosphere plasma, plasma-wave processes, electromagnetic fields and radiation, scientific instrument, space weather.

Contract KII-06-H39/4 Parasitic infections, caused mainly by the speciesTrichinella spiralis(T. spiralis), are widespread around the world and lead to morbidity and mortality in the population. Meanwhile, some studies have showed that these parasites induce oxidative stress in the infected host. With the aim of developing a class of compounds combining anthelmintic with antioxidant properties, a series of new benzimidazolyl-2-hydrazones5a-l, bearing hydroxyl- and methoxy-groups, were synthesized. The anthelmintic activity on encapsulatedT. spiraliswas studiedin vitrothus indicating that all hydrazones were more active than the clinically used anthelmintic drugs albendazole and ivermectin.5band5dkilled the total parasitic larvae (100% effectiveness) after 24 hours incubation period at 37 °C in both concentrations (50 and 100 μg ml−1). The antioxidant activity of the target compounds was elucidatedin vitroagainst stable free radicals DPPH and ABTS as well as iron induced oxidative damage in model systems containing biologically relevant molecules lecithin and deoxyribose. The two 2,3- and 3,4-dihydroxy hydrazones5band5dwere the most effective radical scavengers in all studied systems. DFT calculations were applied to calculate the reaction enthalpies in polar and nonpolar medium and estimate the preferred mechanism of antioxidant activity. The relative radical scavenging ability of compounds5a-lshowed a good correlation to the experimentally observed trends. It was found that the studied compounds are capable to react with various free radicals - ˙OCH3, ˙OOH and ˙OOCH3, through several possible reaction pathways - HAT in nonpolar medium, SPLET in polar medium and RAF in both media. publishersversion published

The idea of sustainable development of tourism is among the most significant trends in this sector globally. In Bulgaria, it is included in the National Strategy for Sustainable Development of Tourism in the Republic of Bulgaria. In the current economic, health and social situation, interest in the sustainable development of destination Bulgaria has strengthened. The current situation creates conditions to update and improve the product portfolio of destination Bulgaria, focusing efforts on using the possibilities of alternative forms of tourism, which find their interpretation in the tourist regionalization of the country and the formation of tourist routes with specialized destinations. The research aims to confirm the possibility of sustainable development of destination Bulgaria through the use of products related to alternative forms of tourism. The study object is the tourism destination Bulgaria’s sustainable development. For the needs of the research, standard scientific methods are used. The stated research tasks support the thesis that the use of specialized forms of tourism in the formation of the product portfolio of destination Bulgaria can contribute to its sustainable development. As a result, the need to use the potential of destination management organizations and the importance of sustainability certification systems is confirmed.

Parasitic infections, caused mainly by the species

The PURPOSE of the present study was to investigate the changes in the size of skeletal muscle fibres and extracellular matrix (ECM) after submaximal training and androgen receptor blocker (ARB) treatment. METHODS: Two groups of animals were used: trained (T) and non-trained (NT). Half of the trained (T+F) and untrained (NT+F) rats were treated with the ARB Flutamide. RESULTS: The analysis of the muscle fibre cross-sectional areas (CSA) of soleus (Sol), extensor digitorum longus (EDL) and gastrocnemius (Gas) showed that trained rats had larger CSA than non-trained. ARB application significantly reduced CSA of EDL and Gas in the trained animals. ARB had no effect of on the amount of ECM in Sol and EDL after training, while in Gas the amount was greater than in the trained controls. CONCLUSIONS: The reduction in the CSA of EDL and Gas muscle fibres is probably due to the higher content of type II fibres, which are more sensitive to androgens. The unchanged amount of ECM in Sol and EDL of the ARB-treated and trained rats suggested a lack of androgen effect. The ECM remodelling in Gas following endurance training is androgen-dependent.

Extracts of medicinal plants are often used for preparation of food supplements, pharmaceutical products or for direct preparation of teas, but they may contain toxic substances, such as polycyclic aromatic hydrocarbons (PAHs). The content of PAHs was determined in Matricaria chamomilla L., Thymus serpyllum L., Tilia tomentosa Moench, Sambucus nigra L. and Achillea millefolium L., collected from urban and rural region near Varna, Bulgaria. The aim of this study was to compare the levels of PAHs in traditionally used medicinal plants from different regions to assess environmental pollution. Benzo[a]anthracene, chrysene, benzo[b]fluoranthene and benzo[a]pyrene are among the 16 priority pollutants pointed out by The United States Environmental Protection Agency. The PAH levels were determined in extracts of medicinal plants by GC-MS after purification. Chrysene was registered as most abundant compound in all the plant species investigated. Benzo[a]pyrene, identified by the International Agency for Research on Cancer (IARC) as carcinogenic to humans, was not detected in the samples analyzed. The levels of investigated PAHs were significantly higher in samples from areas with intensive traffic compared to samples from suburban areas. The sum of the four PAHs in all plant species were found in the range of 0.68 (Sambucus nigra L.) to 6.82 µg/kg dw (Tilia tomentosa Moench) and was below the permissible limit of the European commission.

I. Background. In skeletal muscles the sialic acids have a great significance for their functional maintenance and proper structural organization. Our work for the first time described the expressions of ST3Gal, ST6Gal and ST6GalNAc sialyltransferases specific for glycoproteins in mouse skeletal muscles and murine C2C12 myotube cell cultures.II. Methods and Results. Lectin histochemistry, cytochemistry and lectin blot were used to demonstrate the membrane localization and the electrophoretic profiles of α-2,3- and α-2,6-sialylated glycoproteins. The expression levels of sialyltransferases were analyzed by real time RT-PCR and western blot. The enzymes ST6Gal2 and ST6GalNAc1 were not expressed in skeletal muscle tissue and C2C12 myotubes. In both experimental groups mRNAs of the ST3Gal family prevailed over the mRNA expressions of the ST6Gal and ST6GalNAc families. The profiles of STR expressions showed differences between the two experimental groups, illustrated by the absence of expressions of the mRNA for the ST3Gal6 and ST3GalNAc3 enzymes in the C2C12 cell samples and by the different shares of the enzymes ST3Gal3 and ST3Gal4 in both experimental groups. The different patterns of enzyme expressions in both experimental groups corresponded with differences between their α-2,3- and α-2,6-sialylated glycoprotein profiles.III. Conclusions. These results could be a useful addendum to the knowledge concerning the glycosylation of the skeletal muscle tissue. In addition, this report would be helpful and informative for any researches in future where the C2C12 myotube cell cultures will take a place as an experimental model.

This article discusses issues relevant to the 2015 recalibration of the time series of classical solar indices. It shows that the Wolf numbers WN and the group numbers GN are sensitive to the quality of the observations underpinning the reconstructions of the relevant time series, given the intermittent recordings in the 17th and 18th centuries. The authors suggest that research efforts should focus on the compilation of a long series of total sunspot areas (absolute sunspot magnetic flux), because, on the one hand, this series is less sensitive to poor-quality observations, while, on the other hand, it reflects a clear physical index.

Cyclopropane rings are versatile building blocks in organic chemistry. Their synthesis, by the reaction of sulfur ylides with α,β-unsaturated carbonyl compounds, has recently aroused renewed interest after the discovery of efficient catalysis by using (S)-indoline-2-carboxylic acid. In order to rationalize the behavior of this catalyst, MacMillan proposed a directed electrostatic activation (DEA) mechanism, in which the negative carboxylate group interacts with the positive thionium moiety, thus reducing the activation energy and increasing the reaction rate. More recently, Mayr refuted some of MacMillan conclusions, but accepted the DEA mechanism as a justification for the experimental high reaction rates. In contrast, our results indicate that the selectivity obtained in the process seems to result from several strong hydrogen bond interactions between the two reacting species, while no strong evidence for a DEA mechanism was found. We also concluded that the hydrogen bonds don't improve the reaction rate by lowering the activation energy of the rate-determining step, but can do it by promoting efficient reaction trajectories due to long-range complexation of the reagents. Finally, our results confirm that the cyclopropanation reaction occurs by a two-step mechanism, and that the overall enantioselectivity depends on the relative energies of the two steps, averaged by the relative populations of the iminium intermediates that are initially formed in the reaction.

The present research aimed to examine the effect of dietary phytoextracts supplementation on the chemical composition and fatty acid profile in the meat of rainbow trout (Oncorhynchus mykiss W.), cultivated in a recirculation system. The fish were divided into 6 groups: one control (C) and five experimental groups in the food of which phytoextracts of curcumin (EC), paprika (EP), thyme (ET), oregano (EO) and garlic (EG) were added. The inclusion of phytoextracts had no significant effect on growth parameters of fish from EC, EP, ET, EO and EG groups (P>0.05). No statistical differences on water content, protein and lipids were observed in the meat of fish from the control and the experimental groups (P>0.05). Statistically significantly higher value of the dry matter was established in ET group in comparson with C, EC, EP, EO and EG groups (P≤0.001). The values of ash were significantly lower in fish from all experimental groups compared to the control group. The inclusion of phytoextracts did not affect the fatty acid profile of fish from EP, EO and EG groups (P>0.05). Exceptions are EC and ET groups, which had the lowest value of C18:3n-3 α-linolenic compared to those from the control group (P≤0.05, P≤0.001).

The metabolic syndrome (MetS) is a combination of interrelated risk factors which increase the risk of cardiovascular diseases and diabetes mellitus type 2. The increased frequency of that condition and the diseases associated thereof is attributed to the unhealthy dietary behavior during the last decades. There exist combined high-fat and high-carbohydrate diets for the inducement of the disease in rats which successfully imitate the pathology in humans. The reduced aerobic capacity is considered an unfavorable prognostic marker in cardiovascular accidents and as regards longevity. The data obtained indicate a decrease of submaximal running endurance capacity upon application of high-fatcarbohydrate diet as early as the 4th week and a substantial reduction of VO2max in the 16th week. The results show worsening of the aerobic capacity and are concurrent with an increased cardiovascular risk in rats with developed diet-induced obesity. Introduction The metabolic syndrome (MetS) is a combination of interrelated risk factors which increase the risk of cardiovascular diseases and diabetes mellitus type 2. The increased frequency of that condition and the diseases associated thereof is explained by the unhealthy dietary behavior during the last decades [1, 2]. In the study of MetS, dietary, genetic and pharmacologic animal models are used [3, 4, 5, 6, 7, 8, 9]. Combined high-fat and high-carbohydrate diets for inducement of the disease in rats have been developed, which imitate successfully the pathology in humans [10, 11, 12]. They help induce obesity, impaired glucose tolerance, dyslipidemia, endothelial dysfunction, liver and heart muscle damage [10, 11, 12]. The reduced aerobic capacity is considered an unfavorable prognostic marker in cardiovascular accidents and as regards longevity [13, 14]. Aim This study was aimed at examining the change of aerobic capacity in rats on a combined high-fat and high-carbohydrate diet during a period of 16 weeks. It is part of a complex study of changes in certain morphological, functional, and laboratory indices at various stages of MetS inducement. Materials and Methods Animals Male Wistar rats (n=80) with initial body mass of 160-180 g were used. They were maintained at an ambient temperature of 20 o ± 1 oC, controlled humidity, and a 12:12 h lightdark photoperiod. The experimental protocol was approved by the Commission for Ethical Treatment of Animals at the Bulgarian Food Safety Agency. The rats were reared and all experimental procedures were performed according to the recommendations of the European Commission for the protection and humane treatment of laboratory animals. Since running on a treadmill is a skill which the rats should develop and maintain, prior to the experiment all rats were trained three times a week on a treadmill for small test animals (Columbus Instruments, Columbus, Ohio, USA) for 5 min, with a velocity of 27 m/min, at a track inclination of 5o. Such workload induces no training adaptations but familiarizes the rats with treadmill running and allows selection of rats which run spontaneously [15]. This training session is necessary for the conduct of the forthcoming functional tests. Compliant animals were randomized into two groups: a control group on standard rat chow (, n=20), and a dietary manipulated group, which had free access to a combined high-fat-carbohydrate food with added animal fats (D, n=60). During the whole period, all rats were trained on a treadmill for small test animals trice weekly with same intensity as preliminary period. Diet The control group received standard rat chow provided by the vivarium of Plovdiv Medical University and water ad libitum (Table 1). The dietary manipulated group had free access to a combined high-fat-sucrose diet (High-Fat-Sucrose Diet, HFSD) prepared on-site (Table 1). Table1. Basic properties of the food taken during the experiment.

The diastereo- and enantioselectivity obtained experimentally by Enders et all. (Enders, D.; Niemeier, O.; Straver, S. Synlett 2006, 3399-3402) in the amine-catalyzed intramolecular 5-enolexo aldolization of 1,6-dicarbonyl compounds were fully rationalized using density functional theory methods. A polarizable continuum model was used to describe solvent effects. While 6-enolexo aldolizations are well described by Houk's model on the basis of steric and electrostatic contacts, the main factors conditioning the final selectivity in 5-enolexo processes are calculated to be quite different. Thus, the selectivity results from the summation of several small electrostatic contacts with an unexpected HOMO electronic overlapping plus the ring strain of the five-membered ring, whereas steric effects seem to be unimportant. Our results indicate, in contrast with 6-enolexo processes, that high selectivities are not expected in this type of reaction and that the experimental selectivity shall be very dependent on the reaction conditions, as known experimental results seem to suggest. 7-enolendo products are not expected, as they are predicted to be formed by higher energetic transition states. Variable reaction rates, experimentally observed with different catalysts, are suggested to be mainly a result of different catalyst solubilities.

The radical addition to amides derived from chiral 2,5-disubstituted pyrrolidines has been theoretically studied by the use of density functional methods and the results compared with known experimental data. The results agree quite well with those obtained experimentally and allow the full rationalization of the factors influencing the diastereoselectivity. Steric effects are the main factors determining the selectivity, but electronic interactions can also be very important when the attacking alkene is α,β-conjugated, as in acrylic esters or acrylamides. Additions at the α- and β-positions of the amide chain in the auxiliary are subject to different rules, with the former usually yielding high diastereoselectivities both experimentally and theoretically, whereas the latter is theoretically predicted to occur with low selectivity. We fully rationalize these two opposite behaviours and suggest several ways to circumvent this limitation, thus strongly increasing the interest of this type of structure as chiral auxiliaries in radical reactions.

The values of combustion and formation enthalpy for glycolic acid (I) and glycolide (II) were determined by calorimetry. The temperature dependence of vapor pressures of I and II was obtained using the transpiration method, and the sublimation enthalpies were obtained. The enthalpy of melting of I was found by differential scanning calorimetry. Stable conformers were determined by the ab initio (DFT) method, and combinations of the fundamental oscillations and inertia momenta of I and II conformers were calculated. The full and relative energies of the compounds most stable conformers were found by a composite G3MP2 method, and the enthalpies of formation of I and II in the gaseous state were estimated. The values of the thermodynamic properties in the ideal gas state were determined over the range of 0–1500 K. A thermodynamic analysis was performed for the process of preparation of II from I and the formation of polyglycolide (III) from I and II.

The enthalpies of combustion and formation of S-lactic acid at 298.15 K, ΔcHmo(cr.) = −1337.9 ± 0.8 and ΔfHmo(cr.) = −700.1 ± 0.9 kJ/mol, were determined by calorimetry. The temperature dependence of acid vapor pressure was studied by the transpiration method, and the enthalpy of its vaporization was obtained, ΔvapHo(298.15 K) = 69.1 ± 1.0 kJ/mol. The temperature and enthalpy of fusion, Tm (330.4 K) and ΔmHo(298.15 K) = 14.7 ± 0.2 kJ/mol, were determined by differential scanning calorimetry. The enthalpy of formation of the acid in the gas phase was obtained. Ab initio methods were used to perform a conformational analysis of the acid, calculate fundamental vibration frequencies, moments of inertia, and total and relative energies of the stablest conformers. Thermodynamic properties were calculated in the ideal gas state over the temperature range 0–1500 K. A thermodynamic analysis of mutual transformation processes (the formation of SS- and RS(meso)-lactides from S-lactic acid and the racemization of these lactides) and the formation of poly-(RS)-lactide from S-lactic acid and SS- and RS(meso)-lactides was performed.

The values of the combustion and enthalpies of formation for e-caprolactone were determined by means of combustion calorimetry. The vapor pressures of lactone were measured in the range of 283–353 K, and the value of its enthalpy of vaporization was estimated by the transpiration method. Conformational analysis and calculations of the equilibrium structures, inertia moments, and sets of fundamental vibrations was performed by the B3LYP/6-311++G(3 df, 3 pd) quantum-chemical method. The total energies of the most stable lactone conformers were found and ΔfH(g) was estimated using the composite G3MP2 method. The set of fundamental vibrations for the most stable conformers of the compound was developed on the basis of the available experimental IR spectra and calculated vibration frequencies. The values of the thermodynamic properties of e-caprolactone were determined in the ideal ga s state in the range of 0—1500 K. A set of reliable and interconsistent thermodynamic parameters for e-caprolactone was created. Thermodynamic analysis for liquid-phase polymerization of s-caprolactone in the temperature range of 220—500 K was carried out.

The mechanism proposed by Evans for the dialkylaluminum chloride promoted Diels-Alder reaction of cyclopentadiene with alpha,beta-unsaturated N-acyloxazolidinones has been widely used as a basis for the rationalization of the experimental selectivities observed in many different types of reactions in which oxazolidinones or imidazolidinones are used as chiral auxiliaries. In this manuscript we introduce a new and more general model based on molecular modeling and NMR spectroscopy data that avoids several ambiguous concepts raised by the Evans model and fully explains all available experimental data. While the Evans proposal relies on the formation of high-energetic ionic chelates that promote the rotation of the amide bond in the N-acyloxazolidinone molecule, our model is based on the catalysis by means of low-energetic mono- or bicomplexes at the chain and the ring carbonyl groups that are easily observed by NMR spectroscopy measurements. The observed selectivities are explained by a chirality-transfer concept, in which an achiral Lewis acid works as a bridge for the transfer of chirality between a chiral auxiliary and a prochiral reactive center. Different to the Evans proposal, this mechanism fully explains the experimental selectivities for low Lewis acid concentrations, based on the catalysis by means of concurrent monocomplexes at the chain or the ring carbonyl groups, as well as the increased reaction rates and selectivities experimentally observed for high Lewis acid concentrations. The model can be extrapolated to nonchelating and other chelating Lewis acids, thereby allowing for the rationalization of much experimental data that were never explained by the Evans proposal.

In this work, we performed a complex study of the thermodynamic properties of three alkylated γ -lac- tones. We determined their enthalpies of combustion and formation, measured vapor pressures and found the enthalpies of vaporization, and studied their conforma- tional state. The spectral and molecular data were used to calculate the thermodynamic properties of γ -pen- tanolactone ( I ), γ -hexanolactone ( II ), and γ -nonanolac- tone ( III ). Abstract —The enthalpies of formation of γ -pentanolactone ( I ), γ -hexanolactone ( II ), and γ -nonanolactone ( III ) were determined by combustion calorimetry. The enthalpies of vaporization of these lactones were mea- sured by the transfer method. Conformational analysis was performed and equilibrium structures, sets of fun- damental vibrations, moments of inertia, and total energies of the stablest conformers of I , II , and III were cal- culated by the B3LYP/6-311G( d , p ) , G3MP2, and CBS-QB3 methods. The experimental IR spectra and calcu- lated vibrational frequencies were used to obtain sets of fundamental vibrations of the stablest conformations. The thermodynamic properties of I - III in the ideal gas state were determined over the temperature range 0- 1500 K. Additive and quantum-chemical methods were applied to estimate the ∆ f H ° (g) values of a number of γ -lactones. Composite quantum-chemical methods were used to obtain the energies of monomethyl γ -butyro- lactones and estimate their relative stability depending on the position of the methyl substituent in the ring.

The enthalpies of formation of δ-hexanolactone and δ-nonanolactone were determined by combustion calorimetry. Conformational analysis and quantum-chemical calculations of equilibrium structures, fundamental vibrations, moments of inertia, and total energies were performed for δ-pentanolactone (I), δ-hexanolactone (II), and δ-nonanolactone (III) by the B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and G3MP2 methods. The experimental IR spectra and calculated vibrational frequencies were used to suggest the assignment of vibrational frequencies of stable conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. A thermodynamic analysis of mutual isomerization in the gas and liquid phases over the temperature range 298.15–900 K and liquid-phase polymerization of γ- and δ-pentanolactones and 4-pentenoic acid over the temperature range 298.15–500 K was performed.

The enthalpy of formation of liquid 4-pentenoic acid was determined by combustion calorimetry. The vapor pressure and enthalpy of vaporization of the compound were measured by the transfer method over the temperature range 289-324 K. Conformational analysis was performed. The equilibrium structure, funda- mental vibrations, moments of inertia, and total energy of the stablest acid conformers were calculated by the B3LYP/6-311G( d , p ) and G3MP2 quantum-chemical methods. The experimental IR spectrum and calculated vibrational frequencies were used to assign IR bands. The thermodynamic properties of monomeric 4-pentenoic acid in the ideal gas state were calculated over the temperature range 0-1500 K. Additive and quantum-chem- ical methods were used to estimate the ∆ f H ° (g) and ∆ vap H ° values. Close agreement between the calculation results and experimental data was obtained. It was shown that additive and quantum-chemical methods could be used for estimating the enthalpies of formation and vaporization of nonconjugated alkenoic acids.

The infrared (IR) spectra of sulfanilamide 1 and of its azanion (counter ion Na+) 2 have been measured in dimethyl sulfoxide (DMSO) solutions. The density functional theory (DFT) B3LYP 6-31++G(d,p) computations performed adequately describe the experimental spectroscopic data, including the corresponding frequency isotopic shifts. In agreement between theory and experiment, the conversion of sulfanilamide 1 into azanion 2 results in strong frequency decreases of the asymmetrical and symmetrical vibrations of the SO2 group: predicted 122 cm−1, measured 140 cm−1 in solution (total values), as well as in other essential IR spectral changes. According to the computations, the strongest changes in the steric structure take place at and next to the azanionic center. The new (azanionic) charge is distributed, as follows: 0.08e−, 0.23e−, and 0.12e− are delocalized over the amino, phenylene, and sulfonic groups, respectively, and 0.57e− of it remain localized at the azanionic center. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

To ensure traffic safety, pavement conditions should be evaluated and distress (cracks, potholes, etc.) should be timely detected. In recent years, methods based on the analysis of digital images have been proposed to automatically detect pavement distress. However, most of these methods process the images offline and therefore require a large amount of data to be stored until actual processing. To enable real-time analysis of the images and to reduce the amount of stored data, a highly performant and computationally inexpensive implementation of a current analysis method is required. This paper presents a Graphics Processing Unit (GPU) implementation of an image analysis method for pavement distress detection. GPUs have been recently utilized for high-performance computing in diverse scientific fields. The pavement distress detection method presented in this paper is based on the wavelet transform. The implementation is carried out using the Open Computing Language (OpenCL). To evaluate the performance, the method was tested on 30 pavement images. The results show that a significant improvement in performance can be achieved by utilizing GPUs.

The thermo-sensitivity of two new pea (Pisum sativum L.) cultivars—Afila (mutant in the gene transforming leaves into mustaches) and Ranen (mutant for early ripening)—as compared to the control cultivar Pleven-4 to either low (4 °C, T4) or high temperature (38 °C, T38) was investigated by means of chlorophyll (Chl) fluorescence kinetics. The low temperature treatment decreased the photosynthetic activity, measured via a decline of the Chl fluorescence decrease ratios RFd690 and RFd735, and this was mainly due to a decline of the Chl fluorescence decrease parameter Fd and maximum Chl fluorescence Fm. In the new cv. Ranen the RFd ratios at first decreased and increased again after 24-h exposure to 4 °C, indicating its good acclimation ability to low temperature. The cold-induced changes in the photosynthetic performance of all cultivars were reversed after transferring plants back to 23 °C for 48 h. In the Chl and carotenoid (Car) contents no or little changes occurred during the T4 treatment, except for a slight but clear increase of the ratio Chl a/b and a decrease in the ratio Chl/Car. In contrast to this, the T38 treatment for 72 h decreased the RFd ratios more strongly than the T4 exposure did. In fact, an irreversible injury of the photosynthetic apparatus was caused in the control pea cv. Pleven-4 by a 48-h T38 exposure and for the new cv. Afila after a 72-h T38 exposure. In contrast, the cv. Ranen was less and little sensitive to the T38 exposure. In the heat-sensitive cvs. Pleven-4 and Afila, the decrease in RFd values at T38 was associated with a strong decline of the Chl a+b and total Car contents. The Chl a+b decline could also be followed via an increase of the Chl fluorescence ratio F690/F735. Parallel to this, a strong decline of Chl a/b from ca. 3.0 (range 2.85–3.15) to ca. 1.9 (range 1.85–1.95) occurred indicating a preferential decline of the Chl a-pigment proteins but not of the Chl a/b-pigment protein LHC2. In the relatively heat-tolerant cv. Ranen, however, the ratio Chl a/b declined only partially. After the T4 treatment the stress adaptation index Ap was higher in cv. Ranen than in controls and reached in heat-treated Ranen plants almost the starting value indicating a cold and heat stress hardening of the treated plants. The Chl fluorescence parameters and pigment contents were influenced by T38 and T4 treatments in various ways indicating that the mechanisms of low and high temperature injury of the photosynthetic apparatus are different. The new cv. Ranen exhibited a cross tolerance showing a fairly good acclimation ability to both T4 and T38, hence it is a very suitable plant for outdoor growth and for clarification of the acclimation mechanisms to unfavourable temperatures.

The structure and infrared spectra of formonitrile (hydrogen cyanide) and acetonitrile, their anions, and radicals (45 species in all) have been studied by density functional theory (DFT) B3LYP 6-31++G(d,p) calculations. The results obtained have been compared with the literature and original experimental data. The zero-point vibrational energy (ZPVE)-corrected deprotonation energies of the studied (and other) nitriles correlate fairly well (R = 0.94) with their pKa values, measured in dimethyl sulfoxide (DMSO). The theoretical cyano stretching frequencies νCN of the species studied have been found to correlate satisfactorily (R = 0.97) with the experimental ones. The latter correlation can be used for a theoretical estimation of νCN of many nitriles, their anions, and radicals. The geometry parameters for the molecules, calculated by the same theoretical method, practically coincide with those determined experimentally in the gas state. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006

The structural and force field changes, caused by the conversion of the dicyanamide molecule HN(CN)2 into the corresponding azanion −N(CN)2, have been studied by ab initio and DFT 6–31++G(d,p) force field calculations, as well as (for the anion only) on the basis of literature experimental data. The theoretical vibrational and structural indices of the anion are in agreement with those obtained by vibrational spectroscopy and X-ray diffraction analysis. According to MP2 and B3LYP calculations, the conversion of dicyanamide into the azanion results in 83–122 cm−1 decreases in the cyano stretching frequencies (average of νs and νas), 6.3–8.3 fold increases in the corresponding IR integrated intensities (total values) and other essential spectral changes. Again according to the calculations, ca. 0.6 e− of the new (azanionic) charge are delocalized over the two C N groups and ca. 0.4 e− of it remain localized at the azanionic center.

The conversion of 3- and 4-hydroxybenzonitriles (m- and p-cyanophenols) into oxyanions has been followed by IR spectra, ab initio HF, MP2 6-31G(d) and density functional BLYP, B3LYP 6-31G(d) force field calculations. In a general agreement between theory and experiment, the conversion causes a 34 cm−1 frequency decrease in the cyano stretching band, 3.2-fold increase in its integrated intensity and other essential spectral changes in the para-isomer; for the meta-one the corresponding values are 13 cm−1 and 2.3-fold, respectively. According to the calculations, both molecule and anion of 4-hydroxybenzonitrile are more stable (due to the polar resonance) than the corresponding meta-substituted species. The strongest structural changes, caused by deprotonation, are the 0.105 A shortenings of the Ph–O bonds, 0.054 A lengthenings (mean values) of the adjacent CC bonds and essential bond angle changes in the phenylene rings near the oxyanionic centers. In the case of para-isomer these changes are related to the formation of a quasi-para-quinonoidal structure of the phenylene ring in the oxyanion. According to the electronic density analysis, a bit less (Mulliken) or a bit more (natural bond orbital) than halves of the anionic charges remain localized at the oxyanionic centers. Hydrogen bonds have also been discussed.

The structure of diazonium dicyanomethylide (diazodicyanomethane) +N2–C(CN)2−↔N2C(CN)2 has been studied on the basis of ab initio HF, MP2 and DFT BLYP force field calculations, as well as of literature IR spectra and X-ray diffraction structural data. The results have been compared with those obtained for a series of chemical relatives of the title compound, i.e. molecules, push-pull molecules, anions and zwitterions, containing α-dicyano or diazo fragments, and especially substituted ammonium dicyanomethylides and diazomethane +N2–CH2−↔N2CH2. It has been found on the basis of spectral, bond length, bond order and electric charge analyses that the diazonium (or carbanionic, left) canonical form is much more important for the title zwitterion, than the corresponding one for diazomethane. So, the title compound can be named (and considered as) both diazonium dicyanomethylide and dicyanodiazomethane.

The synthesis of 3-amino-2-butenenitrile (diacetonitrile) by base-catalyzed dimerization of acetonitrile was followed by IR spectra, ab initio HF, MP2 and DFT BLYP, B3LYP force field calculations, and correlation analysis. The conversion of diacetonitrile into the anion causes a 67 cm −1 decrease in the cyano stretching frequency, a threefold increase in the corresponding integrated intensity and other strong spectral changes. In agreement between theory and experiment, the isomerization takes place in the intermediate − NC(CH 3 )CH 2 CN→[HNC(CH 3 )CHCN] − rather than in the end (protonation) product HNC(CH 3 )CH 2 CN→H 2 NC(CH 3 )CHCN, due to the essential energy difference between the charge-localized and delocalized anionic intermediates.

We show that the electromagnetic field in an isotropic (dielectric–magnetic) medium that is arbitrarily nonhomogeneous can be represented in terms of two vector potentials that are solutions of a system of two second-order partial differential equations. Furthermore, we derive conditions that permit the reduction of the two vector potentials to a pair of collinear single components and we establish a connection to an alternative solution formalism in terms of scalar Hertz potentials. The reduction involves both the vector potentials and their sources.

In stereoselective radical reactions, it is accepted that the configuration of the radical precursor has no impact on the levels of stereoinduction, as a prochiral radical intermediate is planar, with two identical faces, independently of its origin. However, Sibi and Rheault (J. Am. Chem. Soc. 2000, 122, 8873-8879) remarkably obtained different selectivities in the trapping of radicals originated from two epimeric bromides, catalyzed by chelating Lewis acids. The selectivity rationalization was made on the basis of different conformational properties of each epimer. However, in this paper we show that the two epimers have similar conformational properties, which implies that the literature proposal is unable to explain the experimental results. We propose an alternative mechanism, in which the final selectivity is dependent on different reaction rates for radical formation from each epimer. By introducing a different perspective of the reaction mechanism, our model also allows the rationalization of different chemical yields obtained from each epimer, a result not rationalized by the previous model. Adaptation to other radical systems, under different reaction conditions, is also possible.