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匹配条件: “Oliver Y. Todorov” ,找到相关结果约55135条。
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Study on the Total Coliforms Count and Coli Titter in the Waters of Kardzhali Reservoir, Bulgaria
Oliver Y. Todorov,Ivan I. Iliev,Sonya K. Trifonova
Ecologia Balkanica , 2012,
Abstract: The aim of this study was to examine TC (total coliforms) and coli titter from two sampling stations in the aquatory of Kardzhali Dam Lake and one station in River Arda, in August, 2011. The values of the TC index in the reservoir vary from 1900±674 cfu/100ml in station I, to 1293±194 cfu/100ml in station II, while the TC value of River Arda reaches 1698±134 cfu/100ml. In Reservoir Kardzhali, the smallest volume of water in which Escherichia coli cells were found, varies between 5 and 15 ml, while for the River Arda the value of coli titter is equal to 1. With highest percentage, regarding the presence of microbiological species in the reservoir waters, is the genus Klebsiella (70%), followed by Citrobacter (15%), Enterobacter (10%) and Serratia (5%), respectively represented by the species Klebsiella oxytoca, Citrobacter freundii, Enterobacter cloacae and Serattia marcescens. In the river Arda two genuses were found - Serratia (50%) and Salmonella (50%).
Endoscopic management of large multicompartmental intraventricular arachnoid cyst extending from foramen magnum to foramen of Monro
Yadav Y,Basoor Abhijeet,Todorov Mina,Parihar Vijay
Neurology India , 2010,
Abstract: The treatment options for symptomatic arachnoid cysts are shunting, open craniotomy, and endoscopic fenestration. Endoscopic fenestration of large arachnoid cyst is safe and effective. Postoperative subdural hematoma and intraparenchymal hemorrhage can be avoided by endoscopic fenestration. This technique has the additional advantage of identifying and treating ventricular abnormalities, such as foramen of Monro stenosis and cerebral aqueduct occlusion. This report describes endoscopic dual fenestration in a child with large multicompartmental intraventricular arachnoid cyst extending from foramen magnum to foramen of Monro. The child presented with difficulty to hold the neck in upright position, irritability, vomiting, and large head. Follow-up postoperative magnetic resonance imaging at 3 months showed a significant reduction in size of the cyst. Clinically, the patient showed a gradual improvement at 10 months follow-up. Probably this is the first report of this nature.
$SU_3$ coherent state operators and invariant correlation functions and their quantum group counterparts
H. Sazdjian,Y. S. Stanev,I. T. Todorov
Physics , 1994, DOI: 10.1063/1.531100
Abstract: Coherent state operators (CSO) are defined as operator valued functions on G=SL(n,C), homogeneous with respect to right multiplication by lower triangular matrices. They act on a model space containing all holomorphic finite dimensional representations of G with multiplicity 1. CSO provide an analytic tool for studying G invariant 2- and 3-point functions, which are written down in the case of $SU_3$. The quantum group deformation of the construction gives rise to a non-commutative coset space. We introduce a "standard" polynomial basis in this space (related to but not identical with the Lusztig canonical basis) which is appropriate for writing down $U_q(sl_3)$ invariant 2-point functions for representaions of the type $(\lambda,0)$ and $(0,\lambda)$. General invariant 2-point functions are written down in a mixed Poincar\'e-Birkhoff-Witt type basis.
Modeling of Asphaltene Grading in Oil Reservoirs  [PDF]
Julian Y. Zuo, Oliver C. Mullins, Chengli Dong, Dan Zhang
Natural Resources (NR) , 2010, DOI: 10.4236/nr.2010.11003
Abstract: Reservoir fluids frequently reveal complex phase behaviors in hydrocarbon columns owing to the effects of gravity, thermal diffusion, biodegradation, active charging, water washing, seals leaking, and so on. In addition, the formation compartmentalization often causing discontinuous distributions of fluid compositions and properties makes the proper fluid characterization and reservoir architecture even more challenging yet compelled. The recognition of compositional grading and flow barriers becomes a key to accurate formation evaluation in a cost effective manner. Downhole fluid analysis (DFA) of asphaltene gradients provides an excellent method to delineate the complexity of black oil columns. In this paper, a methodology was developed to estimate downhole asphaltene variations with depths using an equation-of-state (EOS) approach coupled with DFA measurements. DFA tools were used to determine fluid compositions of CO2, C1, C2, C3-C5, C6+, gas-oil ratio (GOR), density and the coloration (optical density) associated with asphaltene contents at downhole conditions. The delumping and characterization procedures proposed by Zuo et al. (2008) were employed to obtain the detailed compositions excluding asphaltenes. In addition, a molar mass distribution of asphaltenes was described by a three-parameter Gamma probability function. The Gaussian quadrature method was used to generate asphaltene pseudocomponents. Five pseudocomponents were employed to represent the normal asphaltene nanoaggregates. Asphaltene distributions in oil columns were computed by tuning the molar mass of asphaltene nanoaggregates against the DFA coloration logs at a reference depth. The methodology was successfully applied to investigate black oil reservoir connectivity (or flow barriers) for offshore field cases. The analysis results were consistent with the subsequent production data and analytical chemistry. Furthermore, for simplicity, it is reasonable to assume that asphaltenes have average properties such as molar mass in entire oil columns. The results obtained in this work demonstrate that the proposed method provides a useful tool to reduce the uncertainties related to reservoir compartmentalization and to optimize the DFA logging during acquisition.
Method for Tentative Evaluation of Membrane Permeability Coefficients for Sodium and Potassium Ions in Unicellular Organisms  [PDF]
Atanas Todorov Atanasov
Open Journal of Biophysics (OJBIPHY) , 2013, DOI: 10.4236/ojbiphy.2013.31A012
Abstract:

The membrane permeability coefficient for sodium and potassium ions in unicellular organisms can be calculated using the data for cell volume, surface and mean generation time during growth and dividing of cells by binary. Accordingly theory of proposed method, the membrane permeability coefficients for passed trough outer cell membrane sodium and potassium ions, is equal to the volume of unicellular organism divided to product between cell surface and mean generation time of cells. The calculated by this way diapason of values overlaps with experimentally measured diapason of values of permeability coefficient for sodium and potassium ions. The deviation between the theoretically calculated and experimentally measured values of permeability coefficient does not exceed one order of magnitude.

Length of Periods in the Nasal Cycle during 24-Hours Registration  [PDF]
Atanas Todorov Atanasov
Open Journal of Biophysics (OJBIPHY) , 2014, DOI: 10.4236/ojbiphy.2014.43010
Abstract:
The periodic congestion and decongestion of the nasal venous sinuses and an alternation of airflow from one side of the nose to the other are known in literature as “nasal cycle”. It is established that nasal cycle during 24-hours registration contains from 4 to 8 time full periods, length of which varies from 0.80 h to 5.75 h. The mean length of all full periods is 2.80 ± 0.17 h. The mean length of full periods of left nostril is 3.07 h and the mean length of periods of right nostril is 2.43 h. The result suggests that there is any asymmetry in length of periods of airflow trough left and right nostrils about 40 min. The longer periods of left nostril can be connected with higher metabolic and functional activity of brain and human organism during active work.
Shot Noise Suppression at Non-integer Conductance Plateaus in a Quantum Point Contact
N. Y. Kim,W. D. Oliver,Y. Yamamoto,Y. Hirayama
Physics , 2003,
Abstract: We study non-equilibrium differential conductance and current fluctuations in a single quantum point contact. The two-terminal electrical transport properties -- differential conductance and shot noise -- are measured at 1.5 K as a function of the drain-source voltage and the Schottky split-gate voltage. In differential conductance measurements, conductance plateaus appear at integer multiples of $2e^2/h$ when the drain-source voltage is small, and the plateaus evolve to a fractional of $2e^2/h$ as the drain-source voltage increases. Our shot noise measurements correspondingly show that the shot noise signal is highly suppressed at both the integer and the non-integer conductance plateaus. This main feature can be understood by the induced electrostatic potential model within a single electron picture. In addition, we observe the 0.7 structure in the differential conductance and the suppressed shot noise around 0.7 ($2e^2/h$); however, the previous single-electron model cannot explain the 0.7 structure and the noise suppression, suggesting that this characteristic relates to the electron-electron interactions.
Gauge Symmetry and Howe Duality in 4D Conformal Field Theory Models
Ivan Todorov
Advances in Mathematical Physics , 2010, DOI: 10.1155/2010/509538
Abstract: It is known that there are no local scalar Lie fields in more than two dimensions. Bilocal fields, however, which naturally arise in conformal operator product expansions, do generate infinite Lie algebras. It is demonstrated that these Lie algebras of local observables admit (highly reducible) unitary positive energy representations in a Fock space. The multiplicity of their irreducible components is governed by a compact gauge group. The mutually commuting observable algebra and gauge group form a dual pair in the sense of Howe. In a theory of local scalar fields of conformal dimension two in four space-time dimensions the associated dual pairs are constructed and classified. 1. Introduction We review results of [1–7] on 4D conformal field theory (CFT) models, which can be summed up as follows. The requirement of global conformal invariance (GCI) in compactified Minkowski space together with the Wightman axioms [8] implies the Huygens principle (3.6) and rationality of correlation functions [1]. A class of 4D GCI quantum field theory models gives rise to a (reducible) Fock space representation of a pair consisting of an infinite-dimensional Lie algebra and a commuting with its compact Lie group . The state space splits into a direct sum of irreducible modules, so that each irreducible representation (IR) of appears with a multiplicity equal to the dimension of an associated IR of . The pair illustrates a interconnects two independent developments: (i) it appears as a reductive dual pair [9, 10], within (a central extension of) an infinite-dimensional symplectic Lie algebra; (ii) it provides a representation theoretic realization of the Doplicher-Haag-Roberts' (DHR) theory of superselection sectors and compact gauge groups, [11, 12]. I will first briefly recall Howe's and DHR's theories, then (in Section 2) I will explain how some 2D CFT technics can be extended to four space-time dimensions (in spite of persistent doubts that this is at all possible). After these preliminaries we will proceed with our survey of 4D CFT models and associated infinite-dimensional Lie algebras which relate the two independent developments. 1.1. Reductive Dual Pairs The notion of a (reductive) dual pair was introduced by Roger Howe in an influential preprint of the 1970s that was eventually published in [10]. It was previewed in two earlier papers of Howe [9, 13], highlightening the role of the Heisenberg group and the applications of dual pairs to physics. For Howe a dual pair, the counterpart for groups and for Lie algebras of the mutual commutants of von Neumann
Cluster categories and their relation to Cluster algebras, Semi-invariants and Homology of torsion free nilpotent groups
Todorov,Gordana;
Revista de la Uni?3n Matem??tica Argentina , 2007,
Abstract: the structure of cluster categories [bmrrt] is well suited for the combinatorics of cluster algebras [fz1] with the main correspondence being between tilting objects and clusters. furthermore it was shown in [iotw] that there is a close relation between domains of virtual semi-invariants and simplicial complexes associated to cluster categories. also the same simplicial complexes associated to cluster categories are related to the igusa-orr pictures in the homology of nilpotent groups.
Y a-t-il démocratie sans participation ?
Antony Todorov
SociologieS , 2009,
Abstract: Dans tous les pays d’Europe on observe une tendance nette à la baisse de la participation électorale, mais avec une différence très visible entre l’Ouest et l’Est. Dans les nouvelles démocraties, qui découvrent les élections pluralistes après presque cinquante ans de régime communiste à parti unique, on observe un niveau de participation électoral plus bas que dans les démocraties établies de l’Ouest, et la baisse est bien plus prononcée pendant les vingt ans qui ont suivi la chute du mur de Berlin, malgré certes de très fortes différences entre les pays de la région. Dans cet article on cherche à savoir pourquoi l’engagement, sous la forme de la participation à la vie politique et aux élections, caractéristique essentielle du régime démocratique, est en évident déclin dans les nouvelles démocraties des PECO (Pays d’Europe centrale et orientale), et moins dans les anciennes démocraties. Les raisons particulières à la région sont liées à son histoire récente communiste, au processus de transition postcommuniste et à son interaction avec des phénomènes plus neufs qui font partie de la mondialisation. Is there democracy without participation?Whilst a net tendency towards lower electoral participation can be observed in all European countries, a very visible difference exists between the West and the East. In the new democracies, those discovering multi party elections after nearly fifty years of sole communist party rule, the decline observed in electoral participation is more important than that observed in Western democracies; moreover, the decline is even more decisive during the twenty years that followed the fall of the Berlin wall in spite of, certainly, some important differences between the countries of the region. This article attempts to establish why commitment to participating in political life and in elections, both essential characteristics of the democratic regime, is in such evident decline in the new PECO democracies whilst being less important in the older democracies. The particular reasons concerning the region studied are linked to its recent communist histoire, to the post-communist transition processes and to its interaction with more recent phenomena inseparable from the globalization process. Puede existir la democrácia sin la participación?En todos los paises europeos se observa claramente la tendencia a la disminución de la participación electoral aunque haya una diferencia muy sensible entre el oeste y el este europeos. En las nuevas democrácias que han descubierto las elecciones pluralistas despues de casi cincuenta a os del r
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