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匹配条件: “Slaveya T. Petrova” ,找到相关结果约117700条。
Biomonitoring Study of Air Pollution with Betula pendula Roth., from Plovdiv, Bulgaria
Slaveya T. Petrova
Ecologia Balkanica , 2011,
Abstract: The present study is a small part of a program for application the methods of passive and active biomonitoring with tree, herbaceous, moss and lichen species for assessment of the anthropogenic factor in urban conditions. All reported results here are preliminary. Betula pendula was studied as a possible biomonitor of air pollution in Plovdiv. Eight sampling sites in the urban roadside, city center and suburban areas were investigated. Chlorophyll content was determined as essential and sensitive physiological parameter. The concentrations of 26 micro and macroelements were analyzed by FAAS and ICPMS. Maximum for chlorophyll was found in the birch leaves from west part of the town, minimum – in these from north part. More significant variations were detected for Ni, Mn, B, Cr, Co, Fe, Bi, Cd, Al, Zn. Highest concentrations of 12 elements were found in the samples, collected from the central area of Plovdiv.
A contibution to the knowledge of the trophic spectrum of three lacertid lizards from Bulgaria
Ivelin Mollov,Slaveya Petrova
Journal of BioScience and Biotechnology , 2013,
Abstract: A study on the trophic spectrum of three species of lacertid lizards (Lacerta agilis, Lacerta trilineata and Podarcis muralis) was carried out, based on 20 specimens collected in the period 1967-1973 in various localities in Bulgaria. The analyzed data showed that the insects (Insecta) are the most numerous and the most frequently met among the alimentary components of the total amount of food of the studied stomachs (except for Lacerta agilis, where spiders are slightly predominating). The non-insect components consisted spiders and isopods. The largest niche breadth was recorded in Lacerta trilineata (8.25), followed by Podarcis muralis (5.20) and Lacerta agilis (3.44). The niche overlap between the three species (pair-wise comparison) showed medium values and in our opinion there should not be any serious competition for food resources at the places withsympatric distribution.
Horse chestnut (Aesculus hippocastanum L.) as a biomonitor of air pollution in the town of Plovdiv (Bulgaria)
Journal of BioScience and Biotechnology , 2012,
Abstract: The present study is a small part of a program for application the methods of passive and active phytomonitoring with herbaceous species, trees, mosses and lichens for assessment of the anthropogenic factor in urban conditions. Aesculus hippocastanum L. was studied as a possible biomonitor of air pollution with heavy metals and toxic elements in the town of Plovdiv (Bulgaria). Concentrations of Cd, Cr, Cu, Pb, V and U in leaf samples from urban areas with different anthropogenic impact were compared. Motor transport was found to be the major source of contaminants. It was found the significant contribution of some factors as urban gradient, canyon-street effect and wind rose in forming the urban air quality.
Eco-physiological Study on the Influence of Contaminated Waters from the Topolnitza River Catchment Area on Some Crops
Iliana Velcheva,Slaveya Petrova,Violeta Dabeva,Diliyan Georgiev
Ecologia Balkanica , 2012,
Abstract: The present study is a small part of a program for an investigation of the water conditions in the Topolnitza Dam Lake, Topolnitza River and its catchment area. The sensitivity of seeds and young wheat, sunflower and mustard plants to heavy metal stress was examined at laboratory conditions. Our results showed that seedling growth was more sensitive to heavy metals in comparison to seed germination. The length of shoot and root has been adversely affected due to water contamination when compared to the control. A certain negative effect on the photosynthetic pigments content was registered.
Revisiting the Effects of Economic Incentives on Motivation  [PDF]
Kameliia Petrova
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.22041
Abstract: This paper presents a formal framework for modeling the effects of economic incentives on motivation. While economic models represent the utilities from monetary incentives and private benefits in an additive form, studies in psychology show that extrinsic and intrinsic motivation are non-additive and that there exists a continuum between the two. To accommodate for possible interaction effects, a non-additive probability model and evidence theory have been used in the principal-agent set-up. The model produces results consistent with prior evidence presented in social psychology studies.
Some Remarks to Numerical Solutions of the Equations of Mathematical Physics  [PDF]
Ludmila Petrova
American Journal of Computational Mathematics (AJCM) , 2013, DOI: 10.4236/ajcm.2013.33029

The equations of mathematical physics, which describe some actual processes, are defined on manifolds (tangent, a companying or others) that are not integrable. The derivatives on such manifolds turn out to be inconsistent, i.e. they don’t form a differential. Therefore, the solutions to equations obtained in numerical modelling the derivatives on such manifolds are not functions. They will depend on the commutator made up by noncommutative mixed derivatives, and this fact relates to inconsistence of derivatives. (As it will be shown, such solutions have a physical meaning). The exact solutions (functions) to the equations of mathematical physics are obtained only in the case when the integrable structures are realized. So called generalized solutions are solutions on integrable structures. They are functions (depend only on variables) but are defined only on integrable structure, and, hence, the derivatives of functions or the functions themselves have discontinuities in the direction normal to integrable structure. In numerical simulation of the derivatives of differential equations, one cannot obtain such generalized solutions by continuous way, since this is connected with going from initial nonintegrable manifold to integrable structures. In numerical solving the equations of mathematical physics, it is possible to obtain exact solutions to differential equations only with the help of additional methods. The analysis of the solutions to differential equations with the help of skew-symmetric forms [1,2] can give certain recommendations for numerical solving the differential equations.

The Peculiarity of Numerical Solving the Euler and Navier-Stokes Equations  [PDF]
Ludmila Petrova
American Journal of Computational Mathematics (AJCM) , 2014, DOI: 10.4236/ajcm.2014.44026
Abstract: The analysis of integrability of the Euler and Navier-Stokes equations shows that these equations have the solutions of two types: 1) solutions that are defined on the tangent nonintegrable manifold and 2) solutions that are defined on integrable structures (that are realized discretely under the conditions related to some degrees of freedom). Since such solutions are defined on different spatial objects, they cannot be obtained by a continuous numerical simulation of derivatives. To obtain a complete solution of the Euler and Navier-Stokes equations by numerical simulation, it is necessary to use two different frames of reference.
Bound and periodic solutions of the Riccati equation in Banach space
A. Ya. Dorogovtsev,T. A. Petrova
International Journal of Stochastic Analysis , 1995, DOI: 10.1155/s1048953395000189
Abstract: An abstract, nonlinear, differential equation in Banach space is considered. Conditions are presented for the existence of bounded solutions of this equation with a bounded right side, and also for the existence of stationary (periodic) solutions of this equation with a stationary (periodic) process in the right side.
New Late Pleistocene locality of the Alpine Ibex (Capra ibex L.) (Mammalia: Bovidae) in Bulgaria
ZooNotes , 2010,
Abstract: There were a total of 12 localities of fossil Alpine Ibex (Capra ibex) in Bulgaria till now, all of Late Pleistocene. Most of them were from the West part of Stara Planina Mountain. The paper reports the easternmost cave locality of this species from the Pchena Cave (Tvardishki Balkan area, Stara Planina Mnt.), near the town of Tvarditsa. The find represents a cranial fragment, bearing the horn shafts.
How Did the Yakuts Fortify Themselves against the Cold?  [PDF]
Svetlana Ivanovna Petrova
Open Journal of Social Sciences (JSS) , 2015, DOI: 10.4236/jss.2015.33017
Abstract: This article is dedicated to the analysis of the heat-insulating function of winter clothes and personal cold-protective equipments (protectors), which grew out of use at the beginning of the XX century and now are kept in different museum funds. The author pays the main attention to the description of the material, production technologies, and functional heat-insulating properties of the traditional winter clothes and protectors. The article also discusses ethnocultural parallels of the traditional clothes.

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