This work focuses on an integrated approach for lake ecological status assessment, elaborated according to the requirements of the European Water Framework Directive (WFD). Data from five lowland and semi-mountain lak...This work focuses on an integrated approach for lake ecological status assessment, elaborated according to the requirements of the European Water Framework Directive (WFD). Data from five lowland and semi-mountain lakes in Bulgaria (Southeast Europe) collected from two years (2011-2012) form the basis for an integrated assessment and the definition of reference conditions. Several metrics were applied in combination, to classify lakes into five ecological status classes. Assemblages of aquatic organisms: phytoplankton, macrophytes and benthic macroinvertebrates, together with 11 supporting physico-chemical parameters were studied. The assessed unique conditions suggested that reference conditions of Bulgarian lakes have natural variability. This first baseline study illustrated specific cases within the lake types that should be assessed in details before providing standardized classification systems in compliance with the requirements of WFD.展开更多
How can music be a modus of accomplishing what Husserl calls“a radical,skeptical epochē”,that is,a way of refraining from judgment about all that is to be known?In order to answer the question,we have to first subm...How can music be a modus of accomplishing what Husserl calls“a radical,skeptical epochē”,that is,a way of refraining from judgment about all that is to be known?In order to answer the question,we have to first submit music itself to the act of epochē.This will allow us to get free from the widespread opinion that music is only an art,and to understand it in a broad sense,namely as a sphere of Being.This sphere is founded on the tone which,on its part,is thinkable not as an expression of the number(as in the Pythagorean tradition)or a medium for voicing,supplementing,or accompanying words,but as a primary essence enabling us to reach the truth of Being in a direct and immediate way.Hence,music provides an advantage for the one who chooses it as a way of accomplishing epochē.In providing immediate access to the truth of all thinkable things and of Being itself,it releases him from the necessity to cover any distance to it by passing through concepts,notions,and ideas in relation to which he is required to exercise the discipline of epochē.展开更多
The best way to check the validity of our theories(models)is by direct comparison with the experiment(observations).However,this process suffers from numerical inaccuracies,which are not frequently studied and often r...The best way to check the validity of our theories(models)is by direct comparison with the experiment(observations).However,this process suffers from numerical inaccuracies,which are not frequently studied and often remain mostly unknown.In this study,we focus on addressing the numerical inaccuracies intrinsic to the process of comparing theory and observations.To achieve this goal,we built four-dimensional(4D)spectral grids for Wolf–Rayet stars(WC and WN spectral classes)and blue supergiants characterized by low metallicity similar to that of the Small Magellanic Cloud.In contrast to lighter(three-dimensional)grids,which rely on a priori assumptions about certain stellar parameters(e.g.,wind velocity)and thus have limited applicability,our 4D grids vary four independent parameters,enabling more flexible and broadly applicable spectral fitting.Utilizing these 4D grids,we developed and validated a fitting approach facilitating direct fits to observed spectra.Through rigorous testing on designated“test”models,we demonstrated that the numerical precision of derived essential stellar parameters,including effective temperature,mass-loss rate,luminosity,and wind velocity,is better than 0.05 dex.Furthermore,we explored the influence of unaccounted factors,including variations in the metal abundances,wind acceleration laws,and clumping,on the precision of the derived parameters.The results indicate that the first two factors have the strongest influence on the numerical accuracy of the derived stellar parameters.Variations in abundances predominantly influenced the mass-loss rate for weak-wind scenarios,while effective temperature and luminosity remained robust.We found that the wind acceleration law influences the numerical uncertainty of the derived wind parameters mostly for models with weak winds.Interestingly,different degrees of clumping demonstrated good precision for spectra with strong winds,contrasting with a decrease in the precision for weak-wind cases.We found also that the accuracy of our approach depends on spectral range and the inclusion of ultraviolet spectral range improves the precision of derived parameters,especially for an object with weak winds.展开更多
Symplectic symmetry approach to clustering(SSAC)in atomic nuclei,recently proposed,is modified and further developed in more detail.It is firstly applied to the light two-cluster^(20)Ne+αsystem of^(24)Mg,the latter e...Symplectic symmetry approach to clustering(SSAC)in atomic nuclei,recently proposed,is modified and further developed in more detail.It is firstly applied to the light two-cluster^(20)Ne+αsystem of^(24)Mg,the latter exhibiting well developed low-energy K^(π)=0_(1)^(+),k^(π)=2_(1)^(+) and π^(π)=0_(1)^(-) rotational bands in its spectrum.A simple algebraic Hamiltonian,consisting of dynamical symmetry,residual and vertical mixing parts is used to describe these three lowest rotational bands of positive and negative parity in^(24)Mg.A good description of the excitation energies is obtained by considering only the SU(3)cluster states restricted to the stretched many-particle Hilbert subspace,built on the leading Pauli allowed SU(3)multiplet for the positive-and negative-parity states,respectively.The coupling to the higher cluster-model configurations allows us to describe the known low-lying experimentally observed B(E2)transition probabilities within and between the cluster states of the three bands under consideration without the use of an effective charge.展开更多
Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of thes...Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of these materials under uniaxial compression. A simplified model is proposed from experimental observations to describe the connection between the neighboring spheres, which greatly improves the computation efficiency. The effects of the governing physical and geometrical parameters are evaluated; whilst a special attention is paid to the plateau stress, which is directly related to the energy absorbing capacity. Finally, the empirical functions of the relative material density are proposed for the elastic modulus, yield strength and plateau stress for FCC packing arrangement of hollow spheres, showing a good agreement with the experimental results obtained in our previous study.展开更多
The effect of the addition of small amounts of rare earths （Ln=La, Ce, Nd and Gd） to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was inves...The effect of the addition of small amounts of rare earths （Ln=La, Ce, Nd and Gd） to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/AI catalyst were prepared and characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, atomic absorption spectroscopy （AAS）, scanning electron mieroscopy-energy dispersive spectroscopy （SEM-EDS）, H2-temperature-programmed reduc- tion （H2-TPR）, electron paramagnetic resonanee （EPR） spectroscopy and low temperature nitrogen adsorption, The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial re- duction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/CuCo/A1 catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/CuCo/A1 and Nd/CuCo/A1 were the most active catalysts. The catalyst Ce/CuCo/AI was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu＋/Cu2＋ and Ce3＋/Ce4＋. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.展开更多
Functionally graded materials, including their characterization, properties and production methods are a new rapidly developing field of materials science. The aims of this review are to systematize the basic producti...Functionally graded materials, including their characterization, properties and production methods are a new rapidly developing field of materials science. The aims of this review are to systematize the basic production techniques for manufacturing functionally graded materials. Attention is paid to the principles for obtaining graded structure mainly in the metal based functionally graded materials. Several unpublished results obtained by the authors have been discussed briefly. Experimental methods and theoretical analysis for qualitative and quantitative estimation of graded properties have also been presented. The article can be useful for people who work in the field of functionally graded structures and materials, and who need a compact informative review of recent experimental and theoretical activity in this area.展开更多
According to the minimal criteria of the International Society of Cellular Therapy, mesenchymal stem cells(MSCs) are a population of undifferentiated cells defined by their ability to adhere to plastic surfaces when c...According to the minimal criteria of the International Society of Cellular Therapy, mesenchymal stem cells(MSCs) are a population of undifferentiated cells defined by their ability to adhere to plastic surfaces when cultured under standard conditions, express a certain panel of phenotypic markers and can differentiate into osteogenic, chondrogenic and adipogenic lineages when cultured in specific inducing media. In parallel with their major role as undifferentiated cell reserves, MSCs have immunomodulatory functions which are exerted by direct cell-to-cell contacts, secretion of cytokines and/or by a combination of both mechanisms. There are no convincing data about a principal difference in the profile of cytokines secreted by MSCs isolated from different tissue sources, although some papers report some quantitative but not qualitative differences in cytokine secretion. The present review focuses on the basic cytokines secreted by MSCs as described in the literature by which the MSCs exert immunodulatory effects. It should be pointed out that MSCs themselves are objects of cytokine regulation. Hypothetical mechanisms by which the MSCs exert their immunoregulatory effects are also discussed in this review. These mechanisms may either influence the target immune cells directly or indirectly by affecting the activities of predominantly dendritic cells. Chemokines are also discussed as participants in this process by recruiting cells of the immune systems and thus making them targets of immunosuppression. This review aims to present and discuss the published data and the personal experience of the authors regarding cytokines secreted by MSCs and their effects on the cells of the immune system.展开更多
Many studies demonstrate that conventional anticancer drugs elevate intracellular level of reactive oxygen species （ROS） and alter redox-homeostasis of cancer cells. It is widely accepted that anticancer effect of t...Many studies demonstrate that conventional anticancer drugs elevate intracellular level of reactive oxygen species （ROS） and alter redox-homeostasis of cancer cells. It is widely accepted that anticancer effect of these chemotherapeutics is due to induction of oxidative stress and ROS-mediated apoptosis in cancer. On the other hand, the harmful side effects of conventional anticancer chemotherapy are also due to increased production of ROS and disruption of redox-homeostasis of normal cells and tissues. This article describes the mechanisms for triggering and modulation of apoptosis through ROS-dependent and ROS^independent pathways. We try to answer the question： ＂Is it possible to induce highly specific apoptosis only in cancer cells, without overproduction of ROS, as well as without harmful effects on normal cells and tissues？＂ The review also suggests a new therapeutic strategy for selective killing of cancer cells, without significant impact on viability of normal cells and tissues, by combining anticancer drugs with redox-modulators, affecting specific signaling pathways and avoiding oxidative stress.展开更多
The polyphenol content,antioxidant and antimicrobial activities of the extracts obtained by classical, ultrasonic and Soxhlet extractions from dry aerial parts of two Artemisia species(Artemisia vulgaris and Artemisia...The polyphenol content,antioxidant and antimicrobial activities of the extracts obtained by classical, ultrasonic and Soxhlet extractions from dry aerial parts of two Artemisia species(Artemisia vulgaris and Artemisia campestris)were compared.Ultrasound positively affected the yield of extractive substance and the kinetics of extraction,but the extract obtained by the classical extraction showed the highest antioxidant activities and contained higher total contents of phenolic compounds and flavonoids than the extracts obtained by two other extraction techniques.Both flavonoid aglycones(apigenin,quercetin,quercetin 3,3′-dimethyl ether)and flavonoid glycosides(rutin,hyperoside and kaempferol 3-rhamnoside)were identified by thin layer chromatograph(TLC)analysis in the extracts from both species.A.campestris extracts were richer in quercetin than A.vulgaris and its antimicrobial activity was also better than A.vulgaris.Extracts obtained from both species were found to be more effective on the tested yeasts than bacteria.The kinetics of the total extractive substances,such as phenolic,flavonoids and quercetin extraction,was successfully described by the model of unsteady-state diffusion.展开更多
Finite time blow up of the solutions to Boussinesq equation with linear restoring force and combined power nonlinearities is studied. Sufficient conditions on the initial data for nonexistence of global solutions are ...Finite time blow up of the solutions to Boussinesq equation with linear restoring force and combined power nonlinearities is studied. Sufficient conditions on the initial data for nonexistence of global solutions are derived. The results are valid for initial data with arbitrary high positive energy. The proofs are based on the concave method and new sign preserving functionals.展开更多
Jebba area southwestern Nigeria forms part of the Nigerian basement complex which lies in the Neoproterozoic PanAfrican mobile belt. It is underlain by several lithological units among which is a polydeformed granitic...Jebba area southwestern Nigeria forms part of the Nigerian basement complex which lies in the Neoproterozoic PanAfrican mobile belt. It is underlain by several lithological units among which is a polydeformed granitic gneiss. This rock has been dated by LA-ICP-MS yielding a concordant U-Pb zircon age of 2207 ± 20 Ma indicating the crystallization age of the granite protolith. This early Rhyacian age and its affinity with within-plate granites indicates emplacement during crustal extension and rifting presceding the main phase of the Eburnean orogeny. The strong, early, shear fabric, S1, in the rock is interpreted to be also of Paleoproterozoic age i.e. imprinted during the Eburnean orogeny. The Jebba granitic gneiss is thus correlatable with the widely abundant Paleoproterozoic granitic magmatism now represented by many orthogneisses and documented in other parts of southwestern Nigeria, the West African craton, the Borborema Province, the Gurupi Belt, Sao Luis craton and Sao Francisco craton in Brazil.展开更多
Fe-, Y-Fe-Al- and Y-Ce-Fe- citrates were synthesized in ethylene glycol （EG） medium under conditions similar to those used in the polymerized complex method. Their elemental composition, IR,^ 13C and ^1H NMR, X-ray ...Fe-, Y-Fe-Al- and Y-Ce-Fe- citrates were synthesized in ethylene glycol （EG） medium under conditions similar to those used in the polymerized complex method. Their elemental composition, IR,^ 13C and ^1H NMR, X-ray photoelectron and Mossbauer spectra were studied, and formulae describing their composition were proposed. The complexes contained EG bonded as adduct and ester with citric acid ligand and did not contain ligands with deprotonated alcoholic groups. The complexes consisted of agglomerated spheres, 0.7-3 μm in diameter. The local composition of the products was established by energy dispersive X-ray microanalysis. The comparison of the number of the ligands, their average electrical charge and the esterification degree of mono-, di- and trimetallic complexes proved the mixed-metal nature of the species studied. The thermal decomposition of the complexes was studied and a general scheme of the processes taking place was proposed. Highly crystalline, phase homogeneous YaFe4AlO12 was produced after heating the respective complex at 1000 ℃. Ce-doped yttrium-iron garnet, similarly prepared, contained traces of CeO2.展开更多
The paper aims to present a concise overview of the current status of the national spatial data infrastructures(SDI)of the European Union(EU)member states combined with specific peculiarities for Bulgaria.Some major c...The paper aims to present a concise overview of the current status of the national spatial data infrastructures(SDI)of the European Union(EU)member states combined with specific peculiarities for Bulgaria.Some major challenges within the progress of the EU SDIs establishing,which is regulated by the European Directive INSPIRE(Infrastructure for spatial information in Europe)toward establishment of a SDI for environmental policies and activities,are marked out.Available comparative analyses of the main indicators for metadata,data-sets,and data services provided by EU member states are briefly discussed as a special attention is given to the Bulgarian progress.Recent achievements on accelerating the process of implementing the recommendations of the INSPIRE Directive in Bulgaria are outlined.展开更多
Background: On the analogy of the non-pathogenic microbiota found in oral cavity, skin and gastrointestinal tract, existence of blood microbiota was confirmed by DNA sequencing, but never deeply characterized. Hypothe...Background: On the analogy of the non-pathogenic microbiota found in oral cavity, skin and gastrointestinal tract, existence of blood microbiota was confirmed by DNA sequencing, but never deeply characterized. Hypothesis for the existence of dormant blood microbiota in healthy humans have been arisen and single species have been isolated. The aim of our study was to resuscitate and investigate the biodiversity of bacterial and fungal dormant blood microbiota in healthy individuals by blood culturing and NGS DNA sequencing. Results: Twenty eight blood samples of healthy individuals, seven for each blood type, were studied. Several culture media were tested. Blood microbiota resuscitation was performed in BHI broth supplemented with vitamin K 1 mg/ml, 2% sucrose, 0.25% sodium citrate and 0.2% yeastolate at 43?C for 72 h. All tested blood samples were culture positive, as confirmed by Gram staining and TEM. TEM images demonstrated well defined cell structures. Analysis for bacterial and eukaryotic species was performed by 16S rRNA and ITS2 targeted sequencing. The obtained sequences were clustered (≥97% identity) in Operational Taxonomic Units (OTUs). Among cultured and uncultured samples we identified OTUs similarity with 47 bacterial orders belonging to 15 phyla and 39 fungi orders blonging to 2 phyla. For the first time we demonstrated isolation and sequencing identification of fungal blood microbiota in healthy individuals. Blood-group differences were identified among the bacterial microbiome compositions. Conclusion: The dormant blood microbiome is innate of the healthy individuals. Interventional strategies to bind the host blood microbiome with the states of health and disease remain an unmet research goal.展开更多
Young pea plants grown as a water culture were sprayed with hydrogen peroxide and 24 h later were treated with the herbicide paraquat. The effects of paraquat and H2O2 treatment were investigated on the endogenous con...Young pea plants grown as a water culture were sprayed with hydrogen peroxide and 24 h later were treated with the herbicide paraquat. The effects of paraquat and H2O2 treatment were investigated on the endogenous concentrations of free proline, and free and conjugated putrescine, spermidine and spermine. Application of PQ increased the free proline and Put, and decreased conjugated and bound polyamines. The results clearly demonstrate the oxidative damages provoked by PQ application. Single treatment with H2O2 provoked considerable decrease in the free fraction of the three PAs studied 2 h after light exposition, but caused an increase in their respective conjugated fractions. Data suggest that PA changes after H2O2 treatment are due to conversion from free to conjugated form. Three hours later free PAs in H2O2 treated-plants reached control levels;however the conjugated remained higher than the control. No alterations were detected in proline concentration after H2O2 treatment. Pretreatment with Н2О2 activated some component of the plant protection mechanisms by causing an alteration in free/conjugated PAs ratio in plants subsequently subjected to PQ treatment. Data concerning PA and proline concentrations in plants treated with both compounds supposed that H2O2 shows a protective role against PQ and improves the plant tolerance to the oxidative stress generated by paraquat.展开更多
This is a study of the Durand-Kerner and Nourein methods for finding the roots of a given algebraic equation simultaneously. We consider the conditions under which the iterative methods fail. The numerical example is ...This is a study of the Durand-Kerner and Nourein methods for finding the roots of a given algebraic equation simultaneously. We consider the conditions under which the iterative methods fail. The numerical example is presented.展开更多
This research reveals relationships between climate variables and inter-annual dynamics in the area of the glacieret located in the cirque Golemiya Kazan in the Pirin Mountains. The study period is 1993–2017. The cor...This research reveals relationships between climate variables and inter-annual dynamics in the area of the glacieret located in the cirque Golemiya Kazan in the Pirin Mountains. The study period is 1993–2017. The correlations are identified using statistical methods. Also, a statistical model is constructed, including some climate variables as predictors. Despite the evident decrease of the glacieret's size in the period from the 1950 s onwards, the long-term trends for the last decades have been insignificant. The main climatic factors influencing the inter-annual dynamics in the area of the glacieret are air temperature, precipitation, zonal and meridional winds and relative humidity. With respect to the dynamics in the area of the glacieret, the important trends in the different climate variables are those of the warm period air temperatures and zonal(u) wind. They also determine to a great extent its future development by acting in two opposite directions – rising temperatures in the warm period will lead to a rapid decrease of its area by the end of the melting season, while the change of wind directionfrom west to east in the warm period will increase its area. The influence of the zonal wind in the warm period is explained mainly by the location of the glacieret in the cirque. Generally, the glacieret is tilted downwards from west to east. Thus, westerly winds facilitate blowing away the snow from the surface of the glacieret, assisting its melting in the warm period. Easterly winds do not have such an effect. The combination of the opposite effects of these two most important climate variables leads to the most likely scenario for the future development of the glacieret, according to which by the middle of this century it is expected to turn into a semi-permanent snow patch, which disappears after some summers, and by the end of the century to completely melt every year before the end of the melting season.展开更多
A steady-state, rigid-plastic rolling problem for temperature and strain-rate dependent materials with nonlocal friction is considered. A variational formulation is derived, coupling a nonlinear variational inequality...A steady-state, rigid-plastic rolling problem for temperature and strain-rate dependent materials with nonlocal friction is considered. A variational formulation is derived, coupling a nonlinear variational inequality for the velocity and a nonlinear vari- ational equation for the temperature. The existence and uniqueness results are obtained by a proposed fixed point method.展开更多
The Late Devonian-early Carboniferous deposits of the Anarak section in northeastern Isfahan,Central Iran,evaluated based on conodont biostratigraphy,sedimentary environment and sequence stratigraphy.According to the ...The Late Devonian-early Carboniferous deposits of the Anarak section in northeastern Isfahan,Central Iran,evaluated based on conodont biostratigraphy,sedimentary environment and sequence stratigraphy.According to the field observations,five lithological units were identified.Investigating the conodont fauna of the Late Devonian-Carboniferous(Mississippian-Pennsylvanian)deposits of Bahram,Shishtu,and Qaleh(Sardar 1)formations in Anarak section led to the identification of 67 species of 18 conodont genera,and accordingly 22 conodont biozones were differentiated.The correlation of sea-level change curves,regarding to the conodont biofacies with the global sea-level curve,demonstrates the relative correlation in the mentioned times due to the shallow condition of the central Iran basin compared to the European and American basins.The microfacies analysis led to the identification of 12 microfacies related to the open sea,bioclastic barrier,lagoon and tidal flat sub-sedimentary environments in a homoclinal carbonate ramp environment.Based on sequence stratigraphy studies,three 3rd order sequences were identified.The first sequence,which is of the Late Devonian(upper part of the Bahram Formation,32.5 m),the second sequence(12.5 m)is the Late Devonian(uppermost part of the Bahram Formation),and the third sequence(68 m)is the early Carboniferous(the Shishtu I Formation).展开更多
文摘This work focuses on an integrated approach for lake ecological status assessment, elaborated according to the requirements of the European Water Framework Directive (WFD). Data from five lowland and semi-mountain lakes in Bulgaria (Southeast Europe) collected from two years (2011-2012) form the basis for an integrated assessment and the definition of reference conditions. Several metrics were applied in combination, to classify lakes into five ecological status classes. Assemblages of aquatic organisms: phytoplankton, macrophytes and benthic macroinvertebrates, together with 11 supporting physico-chemical parameters were studied. The assessed unique conditions suggested that reference conditions of Bulgarian lakes have natural variability. This first baseline study illustrated specific cases within the lake types that should be assessed in details before providing standardized classification systems in compliance with the requirements of WFD.
基金financial support of the Scientific Research Fund attached to the Bulgarian Ministry of Education and Science within the framework of scientific project No.10/6,15.12.2016“Contemporary musical composition,theory and philosophy”.
文摘How can music be a modus of accomplishing what Husserl calls“a radical,skeptical epochē”,that is,a way of refraining from judgment about all that is to be known?In order to answer the question,we have to first submit music itself to the act of epochē.This will allow us to get free from the widespread opinion that music is only an art,and to understand it in a broad sense,namely as a sphere of Being.This sphere is founded on the tone which,on its part,is thinkable not as an expression of the number(as in the Pythagorean tradition)or a medium for voicing,supplementing,or accompanying words,but as a primary essence enabling us to reach the truth of Being in a direct and immediate way.Hence,music provides an advantage for the one who chooses it as a way of accomplishing epochē.In providing immediate access to the truth of all thinkable things and of Being itself,it releases him from the necessity to cover any distance to it by passing through concepts,notions,and ideas in relation to which he is required to exercise the discipline of epochē.
文摘The best way to check the validity of our theories(models)is by direct comparison with the experiment(observations).However,this process suffers from numerical inaccuracies,which are not frequently studied and often remain mostly unknown.In this study,we focus on addressing the numerical inaccuracies intrinsic to the process of comparing theory and observations.To achieve this goal,we built four-dimensional(4D)spectral grids for Wolf–Rayet stars(WC and WN spectral classes)and blue supergiants characterized by low metallicity similar to that of the Small Magellanic Cloud.In contrast to lighter(three-dimensional)grids,which rely on a priori assumptions about certain stellar parameters(e.g.,wind velocity)and thus have limited applicability,our 4D grids vary four independent parameters,enabling more flexible and broadly applicable spectral fitting.Utilizing these 4D grids,we developed and validated a fitting approach facilitating direct fits to observed spectra.Through rigorous testing on designated“test”models,we demonstrated that the numerical precision of derived essential stellar parameters,including effective temperature,mass-loss rate,luminosity,and wind velocity,is better than 0.05 dex.Furthermore,we explored the influence of unaccounted factors,including variations in the metal abundances,wind acceleration laws,and clumping,on the precision of the derived parameters.The results indicate that the first two factors have the strongest influence on the numerical accuracy of the derived stellar parameters.Variations in abundances predominantly influenced the mass-loss rate for weak-wind scenarios,while effective temperature and luminosity remained robust.We found that the wind acceleration law influences the numerical uncertainty of the derived wind parameters mostly for models with weak winds.Interestingly,different degrees of clumping demonstrated good precision for spectra with strong winds,contrasting with a decrease in the precision for weak-wind cases.We found also that the accuracy of our approach depends on spectral range and the inclusion of ultraviolet spectral range improves the precision of derived parameters,especially for an object with weak winds.
文摘Symplectic symmetry approach to clustering(SSAC)in atomic nuclei,recently proposed,is modified and further developed in more detail.It is firstly applied to the light two-cluster^(20)Ne+αsystem of^(24)Mg,the latter exhibiting well developed low-energy K^(π)=0_(1)^(+),k^(π)=2_(1)^(+) and π^(π)=0_(1)^(-) rotational bands in its spectrum.A simple algebraic Hamiltonian,consisting of dynamical symmetry,residual and vertical mixing parts is used to describe these three lowest rotational bands of positive and negative parity in^(24)Mg.A good description of the excitation energies is obtained by considering only the SU(3)cluster states restricted to the stretched many-particle Hilbert subspace,built on the leading Pauli allowed SU(3)multiplet for the positive-and negative-parity states,respectively.The coupling to the higher cluster-model configurations allows us to describe the known low-lying experimentally observed B(E2)transition probabilities within and between the cluster states of the three bands under consideration without the use of an effective charge.
基金The project supported by the Hong Kong Research Grant Council(RGC)(HKUST 6079/00E)the National Natural Science Foundation of China(10532020).
文摘Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of these materials under uniaxial compression. A simplified model is proposed from experimental observations to describe the connection between the neighboring spheres, which greatly improves the computation efficiency. The effects of the governing physical and geometrical parameters are evaluated; whilst a special attention is paid to the plateau stress, which is directly related to the energy absorbing capacity. Finally, the empirical functions of the relative material density are proposed for the elastic modulus, yield strength and plateau stress for FCC packing arrangement of hollow spheres, showing a good agreement with the experimental results obtained in our previous study.
基金Project supported by the European Social Fund(ESF)(BG051PO001-3.3.06-0050)
文摘The effect of the addition of small amounts of rare earths （Ln=La, Ce, Nd and Gd） to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/AI catalyst were prepared and characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, atomic absorption spectroscopy （AAS）, scanning electron mieroscopy-energy dispersive spectroscopy （SEM-EDS）, H2-temperature-programmed reduc- tion （H2-TPR）, electron paramagnetic resonanee （EPR） spectroscopy and low temperature nitrogen adsorption, The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial re- duction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/CuCo/A1 catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/CuCo/A1 and Nd/CuCo/A1 were the most active catalysts. The catalyst Ce/CuCo/AI was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu＋/Cu2＋ and Ce3＋/Ce4＋. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.
文摘Functionally graded materials, including their characterization, properties and production methods are a new rapidly developing field of materials science. The aims of this review are to systematize the basic production techniques for manufacturing functionally graded materials. Attention is paid to the principles for obtaining graded structure mainly in the metal based functionally graded materials. Several unpublished results obtained by the authors have been discussed briefly. Experimental methods and theoretical analysis for qualitative and quantitative estimation of graded properties have also been presented. The article can be useful for people who work in the field of functionally graded structures and materials, and who need a compact informative review of recent experimental and theoretical activity in this area.
文摘According to the minimal criteria of the International Society of Cellular Therapy, mesenchymal stem cells(MSCs) are a population of undifferentiated cells defined by their ability to adhere to plastic surfaces when cultured under standard conditions, express a certain panel of phenotypic markers and can differentiate into osteogenic, chondrogenic and adipogenic lineages when cultured in specific inducing media. In parallel with their major role as undifferentiated cell reserves, MSCs have immunomodulatory functions which are exerted by direct cell-to-cell contacts, secretion of cytokines and/or by a combination of both mechanisms. There are no convincing data about a principal difference in the profile of cytokines secreted by MSCs isolated from different tissue sources, although some papers report some quantitative but not qualitative differences in cytokine secretion. The present review focuses on the basic cytokines secreted by MSCs as described in the literature by which the MSCs exert immunodulatory effects. It should be pointed out that MSCs themselves are objects of cytokine regulation. Hypothetical mechanisms by which the MSCs exert their immunoregulatory effects are also discussed in this review. These mechanisms may either influence the target immune cells directly or indirectly by affecting the activities of predominantly dendritic cells. Chemokines are also discussed as participants in this process by recruiting cells of the immune systems and thus making them targets of immunosuppression. This review aims to present and discuss the published data and the personal experience of the authors regarding cytokines secreted by MSCs and their effects on the cells of the immune system.
文摘Many studies demonstrate that conventional anticancer drugs elevate intracellular level of reactive oxygen species （ROS） and alter redox-homeostasis of cancer cells. It is widely accepted that anticancer effect of these chemotherapeutics is due to induction of oxidative stress and ROS-mediated apoptosis in cancer. On the other hand, the harmful side effects of conventional anticancer chemotherapy are also due to increased production of ROS and disruption of redox-homeostasis of normal cells and tissues. This article describes the mechanisms for triggering and modulation of apoptosis through ROS-dependent and ROS^independent pathways. We try to answer the question： ＂Is it possible to induce highly specific apoptosis only in cancer cells, without overproduction of ROS, as well as without harmful effects on normal cells and tissues？＂ The review also suggests a new therapeutic strategy for selective killing of cancer cells, without significant impact on viability of normal cells and tissues, by combining anticancer drugs with redox-modulators, affecting specific signaling pathways and avoiding oxidative stress.
基金Supported by the Ministry of Science and Environmental Protection,Republic of Serbia(172047)
文摘The polyphenol content,antioxidant and antimicrobial activities of the extracts obtained by classical, ultrasonic and Soxhlet extractions from dry aerial parts of two Artemisia species(Artemisia vulgaris and Artemisia campestris)were compared.Ultrasound positively affected the yield of extractive substance and the kinetics of extraction,but the extract obtained by the classical extraction showed the highest antioxidant activities and contained higher total contents of phenolic compounds and flavonoids than the extracts obtained by two other extraction techniques.Both flavonoid aglycones(apigenin,quercetin,quercetin 3,3′-dimethyl ether)and flavonoid glycosides(rutin,hyperoside and kaempferol 3-rhamnoside)were identified by thin layer chromatograph(TLC)analysis in the extracts from both species.A.campestris extracts were richer in quercetin than A.vulgaris and its antimicrobial activity was also better than A.vulgaris.Extracts obtained from both species were found to be more effective on the tested yeasts than bacteria.The kinetics of the total extractive substances,such as phenolic,flavonoids and quercetin extraction,was successfully described by the model of unsteady-state diffusion.
基金partially supported by Grant No.DFNI I-02/9 of the Bulgarian Science Fund
文摘Finite time blow up of the solutions to Boussinesq equation with linear restoring force and combined power nonlinearities is studied. Sufficient conditions on the initial data for nonexistence of global solutions are derived. The results are valid for initial data with arbitrary high positive energy. The proofs are based on the concave method and new sign preserving functionals.
文摘Jebba area southwestern Nigeria forms part of the Nigerian basement complex which lies in the Neoproterozoic PanAfrican mobile belt. It is underlain by several lithological units among which is a polydeformed granitic gneiss. This rock has been dated by LA-ICP-MS yielding a concordant U-Pb zircon age of 2207 ± 20 Ma indicating the crystallization age of the granite protolith. This early Rhyacian age and its affinity with within-plate granites indicates emplacement during crustal extension and rifting presceding the main phase of the Eburnean orogeny. The strong, early, shear fabric, S1, in the rock is interpreted to be also of Paleoproterozoic age i.e. imprinted during the Eburnean orogeny. The Jebba granitic gneiss is thus correlatable with the widely abundant Paleoproterozoic granitic magmatism now represented by many orthogneisses and documented in other parts of southwestern Nigeria, the West African craton, the Borborema Province, the Gurupi Belt, Sao Luis craton and Sao Francisco craton in Brazil.
文摘Fe-, Y-Fe-Al- and Y-Ce-Fe- citrates were synthesized in ethylene glycol （EG） medium under conditions similar to those used in the polymerized complex method. Their elemental composition, IR,^ 13C and ^1H NMR, X-ray photoelectron and Mossbauer spectra were studied, and formulae describing their composition were proposed. The complexes contained EG bonded as adduct and ester with citric acid ligand and did not contain ligands with deprotonated alcoholic groups. The complexes consisted of agglomerated spheres, 0.7-3 μm in diameter. The local composition of the products was established by energy dispersive X-ray microanalysis. The comparison of the number of the ligands, their average electrical charge and the esterification degree of mono-, di- and trimetallic complexes proved the mixed-metal nature of the species studied. The thermal decomposition of the complexes was studied and a general scheme of the processes taking place was proposed. Highly crystalline, phase homogeneous YaFe4AlO12 was produced after heating the respective complex at 1000 ℃. Ce-doped yttrium-iron garnet, similarly prepared, contained traces of CeO2.
文摘The paper aims to present a concise overview of the current status of the national spatial data infrastructures(SDI)of the European Union(EU)member states combined with specific peculiarities for Bulgaria.Some major challenges within the progress of the EU SDIs establishing,which is regulated by the European Directive INSPIRE(Infrastructure for spatial information in Europe)toward establishment of a SDI for environmental policies and activities,are marked out.Available comparative analyses of the main indicators for metadata,data-sets,and data services provided by EU member states are briefly discussed as a special attention is given to the Bulgarian progress.Recent achievements on accelerating the process of implementing the recommendations of the INSPIRE Directive in Bulgaria are outlined.
文摘Background: On the analogy of the non-pathogenic microbiota found in oral cavity, skin and gastrointestinal tract, existence of blood microbiota was confirmed by DNA sequencing, but never deeply characterized. Hypothesis for the existence of dormant blood microbiota in healthy humans have been arisen and single species have been isolated. The aim of our study was to resuscitate and investigate the biodiversity of bacterial and fungal dormant blood microbiota in healthy individuals by blood culturing and NGS DNA sequencing. Results: Twenty eight blood samples of healthy individuals, seven for each blood type, were studied. Several culture media were tested. Blood microbiota resuscitation was performed in BHI broth supplemented with vitamin K 1 mg/ml, 2% sucrose, 0.25% sodium citrate and 0.2% yeastolate at 43?C for 72 h. All tested blood samples were culture positive, as confirmed by Gram staining and TEM. TEM images demonstrated well defined cell structures. Analysis for bacterial and eukaryotic species was performed by 16S rRNA and ITS2 targeted sequencing. The obtained sequences were clustered (≥97% identity) in Operational Taxonomic Units (OTUs). Among cultured and uncultured samples we identified OTUs similarity with 47 bacterial orders belonging to 15 phyla and 39 fungi orders blonging to 2 phyla. For the first time we demonstrated isolation and sequencing identification of fungal blood microbiota in healthy individuals. Blood-group differences were identified among the bacterial microbiome compositions. Conclusion: The dormant blood microbiome is innate of the healthy individuals. Interventional strategies to bind the host blood microbiome with the states of health and disease remain an unmet research goal.
文摘Young pea plants grown as a water culture were sprayed with hydrogen peroxide and 24 h later were treated with the herbicide paraquat. The effects of paraquat and H2O2 treatment were investigated on the endogenous concentrations of free proline, and free and conjugated putrescine, spermidine and spermine. Application of PQ increased the free proline and Put, and decreased conjugated and bound polyamines. The results clearly demonstrate the oxidative damages provoked by PQ application. Single treatment with H2O2 provoked considerable decrease in the free fraction of the three PAs studied 2 h after light exposition, but caused an increase in their respective conjugated fractions. Data suggest that PA changes after H2O2 treatment are due to conversion from free to conjugated form. Three hours later free PAs in H2O2 treated-plants reached control levels;however the conjugated remained higher than the control. No alterations were detected in proline concentration after H2O2 treatment. Pretreatment with Н2О2 activated some component of the plant protection mechanisms by causing an alteration in free/conjugated PAs ratio in plants subsequently subjected to PQ treatment. Data concerning PA and proline concentrations in plants treated with both compounds supposed that H2O2 shows a protective role against PQ and improves the plant tolerance to the oxidative stress generated by paraquat.
文摘This is a study of the Durand-Kerner and Nourein methods for finding the roots of a given algebraic equation simultaneously. We consider the conditions under which the iterative methods fail. The numerical example is presented.
基金funded by the research project "Current impacts of global changes on evolution of karst (based on the integrated monitoring of model karst geosystems in Bulgaria)"Science Research Fund (Grant No. DN14/10/20.12.2017)+1 种基金funded by the South-west University of Blagoevgrad (grants RP-A 10/15, RP-A 13/17)SRF (SRF 02/70)
文摘This research reveals relationships between climate variables and inter-annual dynamics in the area of the glacieret located in the cirque Golemiya Kazan in the Pirin Mountains. The study period is 1993–2017. The correlations are identified using statistical methods. Also, a statistical model is constructed, including some climate variables as predictors. Despite the evident decrease of the glacieret's size in the period from the 1950 s onwards, the long-term trends for the last decades have been insignificant. The main climatic factors influencing the inter-annual dynamics in the area of the glacieret are air temperature, precipitation, zonal and meridional winds and relative humidity. With respect to the dynamics in the area of the glacieret, the important trends in the different climate variables are those of the warm period air temperatures and zonal(u) wind. They also determine to a great extent its future development by acting in two opposite directions – rising temperatures in the warm period will lead to a rapid decrease of its area by the end of the melting season, while the change of wind directionfrom west to east in the warm period will increase its area. The influence of the zonal wind in the warm period is explained mainly by the location of the glacieret in the cirque. Generally, the glacieret is tilted downwards from west to east. Thus, westerly winds facilitate blowing away the snow from the surface of the glacieret, assisting its melting in the warm period. Easterly winds do not have such an effect. The combination of the opposite effects of these two most important climate variables leads to the most likely scenario for the future development of the glacieret, according to which by the middle of this century it is expected to turn into a semi-permanent snow patch, which disappears after some summers, and by the end of the century to completely melt every year before the end of the melting season.
文摘A steady-state, rigid-plastic rolling problem for temperature and strain-rate dependent materials with nonlocal friction is considered. A variational formulation is derived, coupling a nonlinear variational inequality for the velocity and a nonlinear vari- ational equation for the temperature. The existence and uniqueness results are obtained by a proposed fixed point method.
文摘The Late Devonian-early Carboniferous deposits of the Anarak section in northeastern Isfahan,Central Iran,evaluated based on conodont biostratigraphy,sedimentary environment and sequence stratigraphy.According to the field observations,five lithological units were identified.Investigating the conodont fauna of the Late Devonian-Carboniferous(Mississippian-Pennsylvanian)deposits of Bahram,Shishtu,and Qaleh(Sardar 1)formations in Anarak section led to the identification of 67 species of 18 conodont genera,and accordingly 22 conodont biozones were differentiated.The correlation of sea-level change curves,regarding to the conodont biofacies with the global sea-level curve,demonstrates the relative correlation in the mentioned times due to the shallow condition of the central Iran basin compared to the European and American basins.The microfacies analysis led to the identification of 12 microfacies related to the open sea,bioclastic barrier,lagoon and tidal flat sub-sedimentary environments in a homoclinal carbonate ramp environment.Based on sequence stratigraphy studies,three 3rd order sequences were identified.The first sequence,which is of the Late Devonian(upper part of the Bahram Formation,32.5 m),the second sequence(12.5 m)is the Late Devonian(uppermost part of the Bahram Formation),and the third sequence(68 m)is the early Carboniferous(the Shishtu I Formation).
