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Search Results: 1 - 10 of 726 matches for " György Keglevich "
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The Kabachnik–Fields Reaction: Mechanism and Synthetic Use
Gyrgy Keglevich,Erika Bálint
Molecules , 2012, DOI: 10.3390/molecules171112821
Abstract: The Kabachnik–Fields (phospha-Mannich) reaction involving the condensation of primary or secondary amines, oxo compounds (aldehydes and ketones) and >P(O)H species, especially dialkyl phosphites, represents a good choice for the synthesis of α-aminophosphonates that are of significant importance due to their biological activity. In general, these three-component reactions may take place via an imine or an α-hydroxy-phosphonate intermediate. The monitoring of a few Kabachnik–Fields reactions by in situ Fourier transform IR spectroscopy has indicated the involvement of the imine intermediate that was also justified by theoretical calculations. The Kabachnik–Fields reaction was extended to >P(O)H species, comprising cyclic phosphites, acyclic and cyclic H-phosphinates, as well as secondary phosphine oxides. On the other hand, heterocyclic amines were also used to prepare new α-amino phosphonic, phosphinic and phosphine oxide derivatives. In most cases, the synthesis under solvent-free microwave (MW) conditions is the method of choice. It was proved that, in the cases studied by us, there was no need for the use of any catalyst. Moreover, it can be said that sophisticated and environmentally unfriendly catalysts suggested are completely unnecessary under MW conditions. Finally, the double Kabachnik–Fields reaction has made available bis(phosphonomethyl)amines, bis(phosphinoxidomethyl)amines and related species. The bis(phosphinoxidomethyl)amines serve as precursors for bisphosphines that furnish ring platinum complexes on reaction with dichlorodibenzonitriloplatinum.
Modifications on the Basic Skeletons of Vinblastine and Vincristine
Péter Keglevich,László Hazai,Gyrgy Kalaus,Csaba Szántay
Molecules , 2012, DOI: 10.3390/molecules17055893
Abstract: The synthetic investigation of biologically active natural compounds serves two main purposes: (i) the total synthesis of alkaloids and their analogues; (ii) modification of the structures for producing more selective, more effective, or less toxic derivatives. In the chemistry of dimeric Vinca alkaloids enormous efforts have been directed towards synthesizing new derivatives of the antitumor agents vinblastine and vincristine so as to obtain novel compounds with improved therapeutic properties.
Synthesis of 1,2,3,6-Tetrahydrophosphinine 1-Oxides by Regioselective Reduction of 1,2-Dihydrophosphinine 1-Oxides
Gyrgy Keglevich,Kálmán újszászy,Krisztina Ludányi,áron Sz?ll?sy,László T?ke
Molecules , 1997, DOI: 10.3390/feb97p4
Abstract: Synthesis of 1,2,3,6-tetrahydrophosphinine 1-oxides by regioselective reduction of 1,2-dihydrophosphinine 1-oxides was reported in this communication.
Synthesis of 1,2,3,4,5,6-Hexahydrophosphinine 1-Oxides by Catalytic Hydrogenation of 3-Phosphabicyclo[3.1.0]hexane 3-Oxides
Gyrgy Keglevich,Antal Tungler,Kálmán újszászy,Tibor Novák,László T?ke
Molecules , 1997, DOI: 10.3390/feb97p3
Abstract: Synthesis of 1,2,3,4,5,6-hexahydrophosphinine 1-oxides by catalytic hydrogenation of 3-phosphabicyclo[3.1.0]hexane 3-oxides was reported in this communication.
Dichloridobis(2-methoxydibenzo[c,e][1,2]oxaphosphorine-κP)platinum(II) trichloromethane solvate
Tamás Holczbauer,György Keglevich,Andrea Kerényi,Mátyás Czugler
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809006643
Abstract: The title compound, [PtCl2(C13H11O2P)2]·CHCl3, has a rare PtCl2 bridging of two dibenzooxaphosphorine ligands through the metal atom. The PtII ion is in a slightly distorted square-planar environment. The trichloromethane solvent molecule shows rotational disorder (major occupancy is 0.75) and is placed near to the inversion centre at (1/2, 1/2, 0) in channels parallel to the a axis. The solvent molecule is linked to the complex molecule via intermolecular bifurcated C—H...Cl and C—H...O hydrogen bonds. The crystal structure is further stabilized by π–π interactions involving the benzene rings, with a centroid–centroid distance of 3.658 (8) .
Category Theoretic Properties of the A. Rényi and C. Tsallis Entropies  [PDF]
Gyrgy Steinbrecher, Alberto Sonnino, Giorgio Sonnino
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.72025
Abstract: The problem of embedding the Tsallis, Rényi and generalized Rényi entropies in the framework of category theory and their axiomatic foundation is studied. To this end, we construct a special category MES related to measured spaces. We prove that both of the Rényi and Tsallis entropies can be imbedded in the formalism of category theory by proving that the same basic partition functional that appears in their definitions, as well as in the associated Lebesgue space norms, has good algebraic compatibility properties. We prove that this functional is both additive and multiplicative with respect to the direct product and the disjoint sum (the coproduct) in the category MES, so it is a natural candidate for the measure of information or uncertainty. We prove that the category MES can be extended to monoidal category, both with respect to the direct product as well as to the coproduct. The basic axioms of the original Rényi entropy theory are generalized and reformulated in the framework of category MES and we prove that these axioms foresee the existence of an universal exponent having the same values for all the objects of the category MES. In addition, this universal exponent is the parameter, which appears in the definition of the Tsallis and Rényi entropies. It is proved that in a similar manner, the partition functional that appears in the definition of the Generalized Rényi entropy is a multiplicative functional with respect to direct product and additive with respect to the disjoint sum, but its symmetry group is reduced compared to the case of classical Rényi entropy.
Failure Mechanism of O-Ring Seals under Extreme Operating Conditions  [PDF]
Gyrgy Szabó, Károly Váradi
Modern Mechanical Engineering (MME) , 2018, DOI: 10.4236/mme.2018.81002
Abstract: In this paper the behavior of an O-ring made of NBR rubber was investigated under extreme conditions. The effect of the extreme initial compression, operating pressure and extreme temperature conditions were examined. The rubber material was tested in simple tension, pure shear and equibiaxial tension modes complemented with a Dynamic Mechanical Thermal Analysis (DMTA) to capture the viscoelastic behavior of the material. For the investigation, a large-strain viscoelastic material model was developed by the authors, to take into account the large deformations caused by extreme conditions. Insufficient space during installation causes extreme initial compression consequently leading the material to crack on the contacting outer surfaces. It was found that the excessive strain and friction induced shear stress contributes primarily to this phenomenon. Extreme operating pressure causes the seal to penetrate into the gap between the shaft and the housing. This behavior damages the material and cracks appear on the seal. High strain areas were found in the proximity of the gap in the material. The analysis of the extreme operating temperature showed that during cooling the O-ring can completely loose its ability to seal at -70°C. There are three contributing factors: the speed of cooling, the temperature and the coefficient of thermal expansion.
Thermal-Mechanical Coupled FE Analysis for Rotary Shaft Seals  [PDF]
Gyrgy Szabó, Károly Váradi
Modern Mechanical Engineering (MME) , 2018, DOI: 10.4236/mme.2018.81007
Abstract: The aim of this paper is to model the steady-state condition of a rotary shaft seal (RSS) system. For this, an iterative thermal-mechanical algorithm was developed based on incremental finite element analyzes. The behavior of the seal’s rubber material was taken into account by a large-strain viscoelastic, so called generalized Maxwell model, based on Dynamic Mechanical Thermal Analyses (DMTA) and tensile measurements. The pre-loaded garter spring was modelled with a bilinear material model and the shaft was assumed to be linear elastic. The density, coefficient of thermal expansion and the thermal conductance of the materials were taken into consideration during simulation. The friction between the rotary shaft seal and the shaft was simplified and modelled as a constant parameter. The iterative algorithm was evaluated at two different times, right after assembly and 1 h after assembly, so that rubber material’s stress relaxation effects are also incorporated. The results show good correlation with the literature data, which state that the permissible temperature for NBR70 (nitrile butadiene rubber) material contacting with ~80 mm shaft diameter, rotating at 2600/min is 100°C. The results show 107°C and 104°C for the two iterations. The effect of friction induced temperature, changes the width of the contact area between the seal and the shaft, and significantly reduces the contact pressure.
Hajnal Gyrgy,Jenei Gyrgy
Transylvanian Review of Administrative Sciences , 2012,
Abstract: The Trans-European Dialogue in Public Administration (TED) is an academic event co-organized each year by the two key professional associations of Public Administration in Europe, the European Group on Public Administration (EGPA) and the Network of Institutes and Schools of Public Administration in Central and Eastern Europe (NISPAcee). Each TED focuses on a selected key theme of contemporary public administration, and invites, or accepts contributions of, the leading scholars of the eld.
Some questions of world economic competition
Simon Gyrgy,Simon Gyrgy Jr.
Medjunarodni Problemi , 2008, DOI: 10.2298/medjp0803257s
Abstract: The paper searches for an answer to the following questions: why had the situation in Japan and the European Union situation improved in comparison with the one in United States prior to the first oil price shock; what factors altered this tendency later, especially from the 1990s onwards; what was the role of the international economic conditions in all that? Applying the models of mathematical economics, the authors have proven their main statements by an econometric investigation. The most important conclusion that can be drawn is that in the world economic competition the situation both in Japan and the European Union was primarily determined by the changes in the world economic conditions, chiefly the oil prices in the world market and the exchange rates, what can less be said of the United States.
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