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Quantum Friction

Chinese Physics Letters 2012年第12期29卷 32-35页

作者： Roumen Tsekov Department of Physical Chemistry University of Sofia1164 SofiaBulgaria

The Brownian motion of a light quantum particle in a heavy classical gas is theoretically described and a new expression for the friction coefficient is obtained for arbitrary *** zero temperature it equals the de Broglie momentum of the mean free path divided by the mean free ***,the corresponding mobility of the quantum particle in the classical gas is equal to the square of the mean free path divided by the Planck *** Brownian motion of a quantum particle in a quantum environment is also discussed.

关键词： temperature. quantum Brownian

Mass effect,aneurysms and flow diverters:Is the pipeline embolization device the Lone Virtuoso?Commentary on‘Pipeline embolization device for intracranial aneurysms presenting with mass effect:a large Chinese cohort’by Zhao et al

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Stroke & Vascular Neurology 2024年第4期9卷 457-458页

作者： Alexander Sirakov Georgi Vladev Kristina Sirakova Kristian Ninov Krasimir Minkin Vasil Karakostov Stanimir Sirakov Interventional Radiology University Hospital St Ivan RilskiSofiaBulgaria Medical university of sofia SofiaBulgaria

In the treatment of symptomatic intracranial aneurysms,the study by Zhao et al stands as a notable addition to the growing body of literature.^(1) Their investigation regarding the Pipeline Embolisation Device’s(PED,Covi-dien/Medtronic,Irvine,California,USA)effi-cacy in alleviating mass effect offers valuable insights that further contribute to the evolving landscape of neurointerventional *** applaud the authors for their dedicated efforts in tackling an essential facet of aneu-rysm *** with studies involving extensive cohorts is always enlight-ening,as they ignite discussions and open avenues for fresh research opportunities.

关键词： aneurysm Irvine intracranial

Optimal control of natural resources in mining industry

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International Journal of Mining Science and Technology 2015年第2期25卷 193-198页

作者： Petrov Nikolay Tanev Angel Electrical Engineering Electronics and AutomationTechnical University-Sofia Faculty of Mathematics and Informatics Sofia University

The paper focuses on the optimal control of natural resources in mining industry. The purpose is to pro- pose an optimal extraction series of these resources during the lifetime of the Mine＇s maintenance. Fol- lowing the proposed optimal control model, a sensitivity analysis has been performed that includes the interest rate impact on the optimal solution. This study shows that the increasing of the interest rate sti- mulates faster extraction of the resources. The discounting factor induces that the resource has to be extracted faster hut this effect is counterbalanced by the diminishing returns of the annual cash flow. At higher parameters of ＂alpha＂ close to one of the power function about 80% from the whole resource will be extracted during the first 4 years of object/mine maintenance. An existence of unique positive root with respect to return of investment has been proposed and proved by two ways： by the ＂method of chords＂ and by using specialized software.

关键词： Optimal control Natural resources Interest rate Sensitivity analysis Method of chords

Effects of dopamine D_(1) receptor blockade on the ERG b- and d-waves during blockade of ionotropic GABA receptors

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Eye and Vision 2016年第1期3卷 245-252页

作者： Elka Popova Momchil Kostov Petia Kupenova Department of Physiology Medical University of SofiaSofiaBulgaria

Background:Some data indicate that the dopaminergic and GABAergic systems interact in the vertebrate retina,but the type of interactions is not well ***:In this study we investigated the effect of dopamine D_(1) receptor blockade by 75μM SCH 23390 on the electroretinographic ON(b-wave)and OFF(d-wave)responses in intact frog eyecup preparations and in eyecups where the ionotropic GABA receptors were blocked by 50μM ***’s t-test,One-way repeated measures ANOVA with Bonferroni post-hoc test and Two-way ANOVA were used for statistical evaluation of the ***:We found that SCH 23390 alone significantly enhanced the amplitude of the b-and d-waves without altering their *** effect developed rapidly and was fully expressed within 8-11 min after the blocker *** alone also markedly enhanced the amplitude of the ERG ON and OFF responses and increased their latency *** effect was fully expressed within 25-27 min after picrotoxin application and remained very stable in the next 20 *** effects of SCH 23390 and picrotoxin are similar to that reported in our previous *** SCH 23390 was applied on the background of the fully developed picrotoxin effect,it diminished the amplitude of the b-and d-waves in comparison to the corresponding values obtained during application of picrotoxin ***:Our results demonstrate that the enhancing effect of D_(1) receptor blockade on the amplitude of the ERG b-and d-waves is not evident during the ionotropic GABA receptor blockade,indicating an interaction between these neurotransmitter systems in the frog *** propose that the inhibitory effect of endogenous dopamine mediated by D_(1) receptors on the ERG ON and OFF responses in the frog retina may be due to the dopamine-evoked GABA release.

关键词： Dopamine D_(1)receptors GABA Electroretinogram b-wave d-wave

Effect of autologous serum after amniotic membrane transplantation for persistent corneal ulcers

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International Journal of Ophthalmology(English edition) 2024年第9期17卷 1639-1644页

作者： Rozaliya Hristova Petya Yankova Georgi Markov Alexander Oscar Yani Zdravkov Department of Ophthalmology Medical University SofiaUniversity Hospital AlexandrovskaSofia 1431Bulgaria Department of Clinical Immunology Medical University SofiaUniversity Hospital AlexandrovskaSofia 1431Bulgaria

AIM:To investigate the effect of adding autologous serum eye drops to the postoperative regime after amniotic membrane transplantation for severe persistent corneal ***:Forty eyes of 40 patients with persistent corneal ulcers were randomly assigned to artificial tears(sodium hyaluronate 0.2%,ATs group,n=20)or autologous serum eye drops(ASEDs,n=20)following treatment with amniotic membrane *** slit lamp images were acquired from all patients before and 30d post *** area with fibrovascular tissue was calculated using Image *** corneal sensitivity was assessed by Cochet-Bonnet aesthesiometry before and one month after *** tissue transparency was assessed with a novel optical ***:Mean age of patients was 61.65±16.47y and 57.3±19.11y in the ATs group and ASEDs group,***-two male and 18 female patients were included in the *** improvement in visual acuity was significantly greater in the ASEDs group(0.14±0.04)than the ATs(0.08±0.04;P=0.00046).Cochet-Bonnet aesthesiometry improved significantly after treatment with a similar rate between *** were no statistically significant differences in the area of postoperative fibrovascular tissue between the two groups(P=0.082).The success rate in the two groups was *** difference in densitometry between the ATs and ASEDs group was statistically significant(P=0.042)with greater reduction from baseline in the ASEDS ***:Autologous serum eye drops can lead to better visual acuity,more stable results and improved densitometry and should be considered in the postoperative care following amniotic membrane transplantation.

关键词： autologous serum amniotic membrane ocular surface persistent corneal ulcer

CONTINUOUS DEPENDENCE OF THE SOLUTIONS OF IMPULSIVE DIFFERENTIAL EQUATIONS ON THE INITIAL CONDITIONS AND BARRIER CURVES

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Acta Mathematica Scientia 2012年第3期32卷 1035-1052页

作者： K.G.Dishlieva Faculty of Applied Mathematics and Informatics Technical University of SofiaSofia1756Bulgaria

The basic objects of investigation in this article are nonlinear impulsive dif- ferential equations. The impulsive moments coincide with the moments of meeting of the integral curve and some of the so-called barrier curves. For such type of equations, suf- ficient conditions are found under which the solutions are continuously dependent on the perturbations with respect to the initial conditions and barrier curves. The results are applied to a mathematical model of population dynamics.

关键词： Impulsive differential equations initial condition barrier curves continuous dependence population dynamics

Mathematical modelling of translational motion of rail-guided cart with suspended payload

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2007年第9期8卷 1395-1400页

作者： MITREV Rosen Department of Engineering Logistics Material handling and Construction MachinesTechnical University of SofiaSofia 1000Bulgaria

In this paper modelling of the translational motion of transportation rail-guided cart with rope suspended payload is considered. The linearly moving cart,driven by a travel mechanism,is modelled as a discrete six degrees of freedom (DOF) dynamic system. The hoisting mechanism for lowering and lifting the payload is considered and is included in the dynamic model as one DOF system. Differential equations of motion of the cart elements are derived using Lagrangian dynamics and are solved for a set of real-life constant parameters of the cart. A two-sided interaction was observed between the swinging payload and the travel mechanism. Results for kinematical and force parameters of the system are obtained. A verification of the proposed model was conducted.

关键词： Transportation rail-guided cart Travel mechanism Swinging payload Discrete dynamical model Mathematical model

Fractionation and Soil-Plant Transfer of ^(241)Am in Different Soil Types

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Pedosphere 2015年第2期25卷 212-219页

作者： Boyan TODOROV Rumyana DJINGOVA Faculty of Chemistry and Pharmacy University of Sofia

Monitoring the behavior of radioactive contaminants associated with military applications,nuclear power facilities,and interim storage of radioactive waste materials is of significant concern in radiological *** sequential extraction schemes(SES) for fractionation of ^(241)Am were compared using five different types of soils,Vertisol,Cambisol,Chromic Luvisol,Eutric Fluvisol,and mixed urban soil,collected from different parts of *** results for the exchangeable ^(241) Am were in a wide range and depended on the SES *** ^(241)Am varied from 0.5%to 6%in the exchangeable phase,from 0.5%to 35%in the carbonate phase,from0.4%to 36%in the reducible phase(easily reducible and moderately reducible),from 3%to 17%in the oxidizable phase,and from10%to 50%in the residual *** 100 d of contamination,around 50%of soil ^(241)Am was permanently fixed in the residual *** was strong evidence that the preferable soil phase for ^(241) Am was the carbonate *** transfer factor of ^(241) Am in the soil-plant system depended on ^(241)Am in the easily oxidizable phase(fulvic acid(FA)+humic acid(HA) phase).These confirmed the applicability of the National Institute of Standards and Technology(NIST) sequential extraction scheme for fractionation of soil^(241) Am since it includes extraction of FA+HA phase and then the carbonate phase.

关键词： carbonate fulvic acid humic acid radioactive contaminants sequential extraction scheme soil contamination transfer factor

Mechanochemical Effects　in　Ln_2O_3-Ln(OH)_3-(H_2O)(Ln=La,Nd) System

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Journal of Rare Earths 1997年第2期15卷 20-23页

作者： DimitrTodorovsky AtanasTerziev Faculty of Chemistry University of Sofia Sofia 1126 1 J. Bourchier Av. Bulgaria

The influence of the mechanoactivation in air and in water suspension on the oxides and hydroxides of La and Nd is studied. The activation is carried out at ambient temperature in agate vessels of a Pulverisette 6 ball mill(Fritsch). La and Nd systems have similar behaviours during the activation with certain quantitative differences. The activation in air causes a dehydration of the hydroxides. An activation for 1 h in aqueous suspension leads to complete hydration of La 2O 3(forming hydroxocarbonates) and increases the relative content of Nd(OH) 3 in the respective systems. The mechanochemical effects are compared with the thermally induced changes in the same system.

关键词： Rare earths Hydroxides Oxides Lanthanum Neodymium Thermal analysis Mechanochemistry