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71.
Flavia Stan 《The Ramanujan Journal》2009,20(1):55-67
As a by-product of his work, E. Symeonidis obtained in (Comment. Math. Univ. Carol. 44(3):437–460, 2003) indirect proofs of two interesting special function identities involving Gegenbauer polynomials. In (Muldoon, 2004
) the question of direct proofs was posed. We answer this question by presenting proofs obtained with the help of computer
algebra algorithms based on WZ theory. 相似文献
72.
Partial characterizations of coordinated graphs: line graphs and complements of forests 总被引:1,自引:0,他引:1
Flavia Bonomo Guillermo Durán Francisco Soulignac Gabriel Sueiro 《Mathematical Methods of Operations Research》2009,69(2):251-270
A graph G is coordinated if the minimum number of colors that can be assigned to the cliques of H in such a way that no two cliques with non-empty intersection receive the same color is equal to the maximum number of cliques
of H with a common vertex, for every induced subgraph H of G. Coordinated graphs are a subclass of perfect graphs. The list of minimal forbidden induced subgraphs for the class of coordinated
graphs is not known. In this paper, we present a partial result in this direction, that is, we characterize coordinated graphs
by minimal forbidden induced subgraphs when the graph is either a line graph, or the complement of a forest.
F. Bonomo, F. Soulignac, and G. Sueiro’s research partially supported by UBACyT Grant X184 (Argentina), and CNPq under PROSUL
project Proc. 490333/2004-4 (Brazil).
The research of G. Durán is partially supported by FONDECyT Grant 1080286 and Millennium Science Institute “Complex Engineering
Systems” (Chile), and CNPq under PROSUL project Proc. 490333/2004-4 (Brazil). 相似文献
73.
Padayatti PS Sheri A Totir MA Helfand MS Carey MP Anderson VE Carey PR Bethel CR Bonomo RA Buynak JD van den Akker F 《Journal of the American Chemical Society》2006,128(40):13235-13242
beta-Lactamases are one of the major causes of antibiotic resistance in Gram negative bacteria. The continuing evolution of beta-lactamases that are capable of hydrolyzing our most potent beta-lactams presents a vexing clinical problem, in particular since a number of them are resistant to inhibitors. The efficient inhibition of these enzymes is therefore of great clinical importance. Building upon our previous structural studies that examined tazobactam trapped as a trans-enamine intermediate in a deacylation deficient SHV variant, we designed a novel penam sulfone derivative that forms a more stable trans-enamine intermediate. We report here the 1.28 A resolution crystal structure of wt SHV-1 in complex with a rationally designed penam sulfone, SA2-13. The compound is covalently bound to the active site of wt SHV-1 similar to tazobactam yet forms an additional salt-bridge with K234 and hydrogen bonds with S130 and T235 to stabilize the trans-enamine intermediate. Kinetic measurements show that SA2-13, once reacted with SHV-1 beta-lactamase, is about 10-fold slower at being released from the enzyme compared to tazobactam. Stabilizing the trans-enamine intermediate represents a novel strategy for the rational design of mechanism-based class A beta-lactamase inhibitors. 相似文献
74.
In this paper we prove existence and uniqueness of strong solutions to the homogeneous Neumann problem associated to a parabolic equation with linear growth with respect to the gradient variable. This equation is a generalization of the time-dependent minimal surface equation. Existence and regularity in time of the solution is proved by means of a suitable pseudoparabolic relaxed approximation of the equation and a passage to the limit. 相似文献
75.
Let D be a bounded homogeneous domain in ℂ
n
. In this paper, we study the bounded and the compact weighted composition operators mapping the Hardy space H
∞(D) into the Bloch space of D. We characterize the bounded weighted composition operators, provide operator norm estimates, and give sufficient conditions
for compactness. We prove that these conditions are necessary in the case of the unit ball and the polydisk. We then show
that if D is a bounded symmetric domain, the bounded multiplication operators from H
∞(D) to the Bloch space of D are the operators whose symbol is bounded. 相似文献
76.
Flavia Barone Adalberto Bonincontro Filomena Mazzei Anna Minoprio Francesco Pedone 《Photochemistry and photobiology》1995,61(1):61-67
Abstract— It is well known that the pyrimidine dimers are the main damage produced by UV radiation on the DNA structure. However, while studies on the photoproduct structure have been carried out extensively, uncertainties still exist on the implication that a single damaging event has on the overall conformation. In particular, the extension of the damage influence on the polynucleotide chain is a matter of debate. This problem is especially important to understanding some steps of the repair mechanisms. In this study we performed a chemical-physical characterization of 21 base pair oligonucleotides containing a single thymine dimer in one strand. Thermodynamic parameters were determined by means of thermal denaturation experiments, and static fluorescence measurements were performed to unequivocally define the primary structure-conformation relationship in this specific case. We used hydroxyl radicals, produced by means of γ-irradiation of the sample solution, to detect fine structure changes. Our data show that the introduction of a single thymine dimer might cause only a slight distortion of the helix geometry, as judged by the evaluation of the enthalpic and the entropic terms and by the small changes observed in the binding of ethidium bromide to DNA. The modifications in the sugar phosphate backbone subsequent to the damaging event are especially evident, near the thymine dimer, toward the 5'-end direction in the strand containing the dimer. 相似文献
77.
A clique-transversal of a graph G is a subset of vertices that meets all the cliques of G. A clique-independent set is a collection of pairwise vertex-disjoint cliques. The clique-transversal number and clique-independence number of G are the sizes of a minimum clique-transversal and a maximum clique-independent set of G, respectively. A graph G is clique-perfect if these two numbers are equal for every induced subgraph of G. The list of minimal forbidden induced subgraphs for the class of clique-perfect graphs is not known. In this paper, we present a partial result in this direction; that is, we characterize clique-perfect graphs by a restricted list of forbidden induced subgraphs when the graph belongs to two different subclasses of claw-free graphs. 相似文献
78.
Wm.C. Lane T.H. Edwards James R. Gillis Francis S. Bonomo Frank J. Murcray 《Journal of Molecular Spectroscopy》1984,107(2):306-317
The infrared absorption spectrum of ν2 of H2Se in the region from 885 to 1347 cm?1 was obtained with a resolution limit of 0.025 cm?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 1604 lines for the six isotopomers of H2Se, including 25 lines for the H274Se isotopomer, and have analyzed them using Watson's A-reduced Hamiltonian in the Ir rotational representation. Ground state constants for each of the five most abundant isotopomers were obtained from fits of microwave transitions combined with weighted averaged ground state combination differences formed from the infrared bands (010), (020), (100), and (001). Upper state constants for each of the five most abundant isotopomers were obtained from least-squares fits of the spectral lines of ν2, keeping the ground state constants fixed to the values determined from our ground state fits. An alternate set of ground state constants together with isotopic mass adjustment constants for all six isotopomers was determined by simultaneously fitting all available microwave transitions and infrared ground state combination differences. Keeping this set of ground state constants fixed, a single set of upper state constants and isotopic mass adjustment constants for the ν2 band was determined by a simultaneous fit of infrared spectral lines from all six isotopomers. 相似文献
79.
Concentrations of inhalable particulate matter (PM10), Pb, Zn, Pt, Ce, Cd, Se and of Benzo(a)pyrene (BaP) were determined in three locations near Venice from September 2000 to September 2001. Meteorological conditions were considered during the sampling period. All components showed higher concentrations during winter, except for Cd and Se in the two sites at Mestre. Spatial and temporal variations were observed. There were correlations between Pb and Zn and PM10, Cd and Se, Pb and BaP and, in the main street sampling site, also between BaP and Pt. Their possible sources of emission are discussed on the basis of correlations among elements. 相似文献
80.
Wm.C. Lane T.H. Edwards James R. Gillis Francis S. Bonomo Frank J. Murcray 《Journal of Molecular Spectroscopy》1982,95(2):365-380
The infrared absorption spectrum of ν2 of H2S in the region from 1000 to 1500 cm?1 was obtained with a resolution limit of <0.05 cm?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 387 lines due to H232S, 75 lines due to H234S, and 15 lines due to H233S, and have analyzed them using Typke's reduction of Watson's Hamiltonian. Slightly revised ground-state constants for the 32 isotope were obtained from a simultaneous fit of the microwave transitions observed by Helminger, Cook, and De Lucia, combined with weighted averaged ground-state combination differences formed from the infrared bands (010), (020), (100), (001), (110), (011), (210), and (111). The standard deviation for the fit was 0.0018 cm?1 for the infrared data and 0.000032 cm?1 for the microwave lines. Upper-state constants for the 32 isotope were obtained from a least-squares fit of the spectral lines of ν2, keeping the ground-state constants fixed to the values determined by the combination difference fit. The standard deviation of the (010) line fit was 0.0017 cm?1 for the 32 isotope. Ground-state and upper-state isotopic mass adjustment constants were determined in a simultaneous fit of lines of H233S and H234S, keeping the ground-state and upper-state constants for the 32 isotope fixed. 相似文献