278 research outputs found
Limits of the Classical Concept of Concentration
No full textSolutions of very low concentrations cannot be treated by the usual concept of concentration. Stochastic calculations are performed for the analysis of such solutions containing one or a few molecule(s). It is concluded that these systems escape the usual concentration parameters. Two “case histories” are also shown for demonstration of the practical consequences of the theoretical analysis
Molecular elements of ion permeation and selectivity within calcium channels
No full textVoltage-dependent calcium channels are located in the plasma membrane and form a highly selective conduit by which Ca2+ ions enter all excitable cells and some nonexcitable cells. Extensive characterization studies have revealed the existence of one low (T) and five high-voltage-activated calcium channel types (L, N, P, Q, and R). The high voltage-activated calcium channels have been found to exist as heteromultimers, consisting of an alpha(1), beta, alpha(2)/delta, and gamma subunit. Molecular cloning has revealed the existence of 10 channel transcripts, and expression of these cloned calcium channel genes has shown that basic voltage-activated calcium channel function is strictly carried by the corresponding a, subunits. In turn, the auxiliary subunits serve to modulate calcium channel function by altering the voltage dependence of channel gating, kinetics, and current amplitude, thereby creating a likelihood for calcium channels with multiple properties. Although for calcium channels to be effective, Ca2+ ions must enter selectively through the pore of the alpha(1)-subunit, bypassing competition with other extracellular ions. The structural determinants of this highly selective Ca2+ filter reside within the four glutamic acid residues located at homologous positions within each of the four pore-forming segments. Together, these residues form a single or multiple Ca2+ affinity site(s) that entrap calcium ions, which are then electrostatically repulsed through the intracellular opening of the pore. This mechanism of high-selectivity calcium filtration, the spatial arrangement of pore glutamic acid residues; and the coordination chemistry of calcium binding are discussed in this review
Sperner type theorems with excluded subposets
No full textLet F be a family of subsets of an n-element set. Sperner's theorem says that if there is no inclusion among the members of F then the largest family under this condition is the one containing all ⌊ frac(n, 2) ⌋-element subsets. The present paper surveys certain generalizations of this theorem. The maximum size of F is to be found under the condition that a certain configuration is excluded. The configuration here is always described by inclusions. More formally, let P be a poset. The maximum size of a family F which does not contain P as a (not-necessarily induced) subposet is denoted by La (n, P). The paper is based on a lecture of the author at the Jubilee Conference on Discrete Mathematics [Banasthali University, January 11-13, 2009], but it was somewhat updated in December 2010. © 2011 Elsevier B.V. All rights reserved
Gyula Szekfű: Three generations
No full textTitle: Három nemzedék. Egy hanyatló kor története (Three generations. The history of a decaying epoch) Originally published: Három nemzedék (Budapest: Élet, 1920); revised ed.: Három nemzedék, és ami utána következik (Budapest: Királyi Magyar Egyetemi Nyomda, 1934) Language: Hungarian The excerpts used are from Három nemzedék, és ami utána következik (Budapest: ÁKV-Maecenas, 1989), pp. 301–307. About the author Gyula Szekfű [1883, Székesfehérvár–1955, Budapest]: historian, editor, university ..
Hangzáskép, íráskép - Juhász Gyula : Anna örök
No full textThe author contrasts artistic recitals of Anna örök (Anna is forever), a poem by 20th century Hungarian poet Gyula Juhász (1883-1937). The principled subject of her analysis is the change of rhythm (from iambic to trochaic and vice versa) with regard to enjambment; specifically she examines how the written form is realized in the acoustic form of five reciters' performance
ChemInform Abstract: Dicobalt Hexacarbonyl Derivatives of Chiral Acetylenes.
No full text(mu(2)-RC(2)R')Co-2(CO)(6) complexes are prepared where R not equal R' and one of these substituents is a chiral organic group. The structures of the 11 complexes (10 new) range from the simplest possible chiral acetylenic hydrocarbon derivative (S-3-methyl-1-pentyne 1a) to ethynylsteroid (1f, 1g, 1h) and ethynylcodeine (1i, 1j, 1k) derivatives. The CD spectra are reported and the results are analysed in terms of a quadrant rule. The CD spectra show that in all complexes the Co-2(CO)(6) fragment of the molecule gets chirally perturbed. The reasons for the chiral perturbation include apolar repulsing (dominant for the hydrocarbon acetylenes) and polar attractive (''autosolvation''; dominant for acetylenes with polar hetero-atom containing substituents) forces
On the reactivity of acetylenes coordinated to cobalt, 9. Effects of substitution and coordination on the 13C-NMR chemical shifts of the sp carbons of (R1C2R2)Co2(CO)6 complexes. Molecular structure of (mu2-PhC2SiPh3)Co2(CO)6
No full textThirty-four (mu(2)-R(1)C(2)R(2))Co-2(CO)(6) complexes (14 new) were prepared and characterized by their IR v(CO) and H-1- and C-13-NMR spectra. The C-13-NMR chemical shifts of the coordinated sp carbon atoms were correlated with those of the corresponding free acetylenes. This indicated that the interaction between the R(1) and R(2) groups and the C2Co2(CO)(6) moiety is very sensitive not only to the donor/acceptor character of R(1) and R(2) but also to the orbital symmetry of the atoms attached directly to the C(sp) atoms. The changes of the delta(C-13) values of the C(sp) atoms upon coordination were also analyzed in these terms. It is concluded that although the dinuclear mu(2)-coordination of the acetylene results in a high degree of excitation the stability of the C2Co2(CO)(6) moiety diminished the reactivity of the organic ligand. Differences in the reactivity of the (mu(2)-R(1)C(2)R(2))Co-2(CO)(6) complexes in carbonylation are also discussed. The crystal and molecular structure of (PhC(2)SiPh(3))Co-2(CO)(6) was determined by single crystal X-ray diffraction. This compound crystallizes in the orthorhombic Pbca space group with a = 28.790(2) Angstrom, b = 11.577(1) Angstrom, c = 17.833(2) Angstrom, Z = 8. The structure was determined with R = 0.039, R(w) = 0.036
Adatok a győr-gyirmóti Holt-Rába lepkefaunájához (Lepidoptera)
No full textAfter the sudden death of the primary author of this paper, Gyula János Horváth (1961-2019), the lepidopterologist working around the Szigetköz and Győr his collection has been bought by the Rippl-Rónai Museum (Kaposvár). The documentation of this unpublished research was chosen from his written legacy. It contains significant data and information for the fauna of the Szigetköz. The post-editing and modification was carried out by the secondary author. The primary author publishes the results of his research focusing on nocturnal Micro- and Macrolepdioptera, that was carried out in 2004 around Holt-Rába, next to Győr-Gyirmót. Altogether 532 species were collected, 157 of Micro- and 375 of Macrolepidoptera, respectively. The more valueable and rare species are Cosmopterix orichalcea, Atremaea lonchoptera, Friedlanderia cicatricella, Arenosthola semicana, amongst some protected ones (Ostrinia palustralis, Euplagia quadripunctaria, Catocala fraxini, Xestia sexstrigata)
FE Simulation Of A Cord-Rubber Composite Tube Subjected To Bending Due To Operational Loads On A Railroad Reverse Curve With Extremely Low Curve Radius At Sub-Zero Temperature
No full textAdatok a németlukafai üveghuta történetéhez = Supplementary data for the history of the glasshouse of Németlukafa
No full textIn the 18th and 19th century several glasshouses operated in the forests of Zselic region. One of the most significant ones was in operation between 1799 and 1888 in Németlukafa. The equipment of the faience manufacture, which was working side by side with the glasshouse, was bought by the Zsolnay family of Pécs in the 1850’s and became the first machine line of their factory. The manuscript of the monograph written on the topic by Gyula J. Horváth has disappeared around the time of his death (2003). The present study attempts to save the valuable notes as were left in his heritage and completes it with knowledge of the author
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