OALib Journal期刊

ISSN: 2333-9721




2018 ( 113 )

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2016 ( 356 )

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匹配条件: “Rositsa E. Chilingirova” ,找到相关结果约167102条。
Heavy metals content in soil near non1ferous metals production facility and domestic wastes landfill in the area of Kardzhali town
Rositsa E. Chilingirova,Jeni N. Staykova,Iliana G. Velcheva,Vanya M. Naydenova
Ecologia Balkanica , 2011,
Abstract: The predominant soil types in the region of Kardzhali are maroon forest soils highly leached and poorly podzolized. Most of the soils have medium to high erosion ability IIIII degree, and the pH is neutral to slightly alkaline (77,8). Few are weak and moderate acidic pH (6,75). Soils are mostly shallow to moderately deep, poor in nutrients. In the region of Kardzhali main pollutants are heavy metals from miningprocessing and metallurgical business activities of “GorubsoKardzhali” AD and LZC AD, Kardzhali. In the paper are presented results of soil contamination mainly with lead, cadmium, copper and zinc, showing concentrations of lead in the soil over the MAC, according to Ordinance № 3/2008 Standards for acceptable content of harmful substances in soil.
Instantaneous Switching Processes in Quasi-Linear Circuits
Rositsa Angelova,Todor Gichev
Advances in Electrical and Electronic Engineering , 2004,
Abstract: The paper considers instantaneous processes in electrical circuits produced by the stepwise change of the capacitance of the capacitor and the inductance of the inductor and by the switching on and switching off of the circuit. In order to determine the set of electrical circuits, for which it is possible to explicitly obtain the values of the currents and the voltages at the end of the instantaneous process, a classification of the networks with nonlinear elements is introduced in the paper. The instantaneous switching process in the moment t0 is approximated when T->t0 with a sequence of processes in the interval [t0, T]. For quasi-linear inductive and capacitive circuits; we present the type of the system satisfied by the currents and the voltages, the charges, as well as the fluxes in the interval [t0, T]. From this system, after passage to the limit T->t0, we obtain the formulas for the values of the circuits at the end of the instantaneous process. The obtained results are applied for the analysis of particular processes.
The Assembly of the Plasmodial PLP Synthase Complex Follows a Defined Course
Ingrid B. Müller, Julia Kn?ckel, Matthew R. Groves, Rositsa Jordanova, Steven E. Ealick, Rolf D. Walter, Carsten Wrenger
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0001815
Abstract: Background Plants, fungi, bacteria and the apicomplexan parasite Plasmodium falciparum are able to synthesize vitamin B6 de novo, whereas mammals depend upon the uptake of this essential nutrient from their diet. The active form of vitamin B6 is pyridoxal 5-phosphate (PLP). For its synthesis two enzymes, Pdx1 and Pdx2, act together, forming a multimeric complex consisting of 12 Pdx1 and 12 Pdx2 protomers. Methodology/Principal Findings Here we report amino acid residues responsible for stabilization of the structural and enzymatic integrity of the plasmodial PLP synthase, identified by using distinct mutational analysis and biochemical approaches. Residues R85, H88 and E91 (RHE) are located at the Pdx1:Pdx1 interface and play an important role in Pdx1 complex assembly. Mutation of these residues to alanine impedes both Pdx1 activity and Pdx2 binding. Furthermore, changing D26, K83 and K151 (DKK), amino acids from the active site of Pdx1, to alanine obstructs not only enzyme activity but also formation of the complex. In contrast to the monomeric appearance of the RHE mutant, alteration of the DKK residues results in a hexameric assembly, and does not affect Pdx2 binding or its activity. While the modelled position of K151 is distal to the Pdx1:Pdx1 interface, it affects the assembly of hexameric Pdx1 into a functional dodecamer, which is crucial for PLP synthesis. Conclusions/Significance Taken together, our data suggest that the assembly of a functional Pdx1:Pdx2 complex follows a defined pathway and that inhibition of this assembly results in an inactive holoenzyme.
Academic Education in Library and Information Management in Bulgaria  [PDF]
Rositsa Krasteva, Tereza Trencheva, Sabina Eftimova, Tania Todorova
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.28023
Abstract: The purpose of this publication is to present the contemporary aspects of training educational and qualification degree “Bachelor” of Specialty “Library and Information Management” of the Library Management Department at the State University of Library Studies and Information Technologies (SULSIT) in Sofia, Bulgaria.In view of specificity and completeness of the presented information in this publication there is a limit, which refers to the training only in educational and qualification degree “Bachelor”. The following methods are used: a study of the curriculums of many universities worldwide teaching in this or a related specialty; comparative analysis; synthesis of the obtained information. Accent is put on the disciplines Intellectual Property, Standardization in Library Activities, Quality Management in Library and Information Activities, Library Psychology and Bibliotherapy. The research draws attention to some aspects insufficiently covered in the curriculum of the programs preparing future highly knowledgeable, trained library and information managers, and offers some solutions, based on our experience in the State University of Library Studies and Information Technologies, to the attention of the LIS academic and professional community.
Composition and Structure of Testate Amoebae Fauna (Protozoa: Arcellinida and Euglyphida) in Durankulak Lake (Northeastern Bulgaria)
Rositsa D. Davidova,Victor M. Vasilev
Ecologia Balkanica , 2012,
Abstract: An ecological study of the testate amoebae fauna in Durankulak Lake (Northeastern Bulgaria) revealed 91 taxa, belonging to 20 genera. The genera Difflugia (34 species), Centropyxis (14), Arcella (6) and Difflugiella (6) had the highest species diversity. The species Trinema enchelys (31.2% relative abundance), Euglypha rotunda (15.1%) and Microchlamys patella (6.6%) were present with high population density and were dominants in the lake. The species richness and abundance of testaceans differed considerably among separate localities. By the mean of some basic indices for structure of communities, a characterization of the diversity of testate amoebae was made.
Machine learning and word sense disambiguation in the biomedical domain: design and evaluation issues
Hua Xu, Marianthi Markatou, Rositsa Dimova, Hongfang Liu, Carol Friedman
BMC Bioinformatics , 2006, DOI: 10.1186/1471-2105-7-334
Abstract: Experiments were designed to measure the effect of "sample size" (i.e. size of the datasets), "sense distribution" (i.e. the distribution of the different meanings of the ambiguous word) and "degree of difficulty" (i.e. the measure of the distances between the meanings of the senses of an ambiguous word) on the performance of WSD classifiers. Support Vector Machine (SVM) classifiers were applied to an automatically generated data set containing four ambiguous biomedical abbreviations: BPD, BSA, PCA, and RSV, which were chosen because of varying degrees of differences in their respective senses. Results showed that: 1) increasing the sample size generally reduced the error rate, but this was limited mainly to well-separated senses (i.e. cases where the distances between the senses were large); in difficult cases an unusually large increase in sample size was needed to increase performance slightly, which was impractical, 2) the sense distribution did not have an effect on performance when the senses were separable, 3) when there was a majority sense of over 90%, the WSD classifier was not better than use of the simple majority sense, 4) error rates were proportional to the similarity of senses, and 5) there was no statistical difference between results when using a 5-fold or 10-fold cross-validation method. Other issues that impact performance are also enumerated.Several different independent aspects affect performance when using ML techniques for WSD. We found that combining them into one single result obscures understanding of the underlying methods. Although we studied only four abbreviations, we utilized a well-established statistical method that guarantees the results are likely to be generalizable for abbreviations with similar characteristics. The results of our experiments show that in order to understand the performance of these ML methods it is critical that papers report on the baseline performance, the distribution and sample size of the senses in the dat
Ammonium hydrogen (RS)-[(5-methyl-2-oxo-1,3-oxazolidin-3-yl)methyl]phosphonate
Petar Todorov,Emilia Naydenova,Rositsa P. Nikolova,Boris L. Shivachev
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536809050338
Abstract: In the title compound, NH4+·C5H9NO5P , the five-membered methyloxazolidin-2-one unit is disordered over two positions, the major component having a site occupancy of 0.832 (9). A three-dimensional network of O—H...O and N—H...O hydrogen bonds stabilizes the crystal structure.
Ahmed Jashari,Emil Popovski,Bozhana Mikhova,Rositsa P. Nikolova
Acta Crystallographica Section E , 2013, DOI: 10.1107/s1600536813000858
Abstract: In the title compound, C16H15N3O4, the dihedral angle between the chromane and isoxazole rings [r.m.s. deviations = 0.042 and 0.007 , respectively] is 20.33 (12)°. The molecular geometry is stabilized by an intramolecular N—H...O hydrogen bond. In the crystal, N—H...O hydrogen bonds generate chains along the c-axis direction. The crystal studied was a non-morohedral twin.
(4-Carbamoylphenyl)boronic acid
Margarita D. Apostolova,Rositsa P. Nikolova,Boris L. Shivachev
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810014789
Abstract: In the title compound, C7H8BNO3, the molecule lies on an inversion center leading to a statistical disorder of the B(OH)2 and CONH2 groups. In the crystal structure, molecules are linked by N—H...O and O—H...O hydrogen bonds, forming sheets parallel to the bc plane. The B(OH)2 and CONH2 groups are twisted out of the mean plane of the benzene ring by 23.9 (5) and 24.6 (6)°, respectively.
Humor as a Reward Mechanism: Event-Related Potentials in the Healthy and Diseased Brain
Armand Mensen, Rositsa Poryazova, Sophie Schwartz, Ramin Khatami
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085978
Abstract: Humor processing involves distinct processing stages including incongruity detection, emotional response, and engagement of mesolimbic reward regions. Dysfunctional reward processing and clinical symptoms in response to humor have been previously described in both hypocretin deficient narcolepsy-cataplexy (NC) and in idiopathic Parkinson disease (PD). For NC patients, humor is the strongest trigger for cataplexy, a transient loss of muscle tone, whereas dopamine-deficient PD-patients show blunted emotional responses to humor. To better understand the role of reward system and the various contributions of hypocretinergic and dopaminergic mechanisms to different stages of humor processing we examined the electrophysiological response to humorous and neutral pictures when given as reward feedback in PD, NC and healthy controls. Humor compared to neutral feedback demonstrated modulation of early ERP amplitudes likely corresponding to visual processing stages, with no group differences. At 270 ms post-feedback, conditions showed topographical and amplitudinal differences for frontal and left posterior electrodes, in that humor feedback was absent in PD patients but increased in NC patients. We suggest that this effect relates to a relatively early affective response, reminiscent of increased amygdala response reported in NC patients. Later ERP differences, corresponding to the late positive potential, revealed a lack of sustained activation in PD, likely due to altered dopamine regulation in reward structures in these patients. This research provides new insights into the temporal dynamics and underlying mechanisms of humor detection and appreciation in health and disease.

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