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111.
112.
Tight Distance-Regular Graphs and the Q-Polynomial Property 总被引:1,自引:0,他引:1
Arlene A. Pascasio 《Graphs and Combinatorics》2001,17(1):149-169
Let Γ denote a distance-regular graph with diameter d≥3, and assume Γ is tight (in the sense of Jurišić, Koolen and Terwilliger). Let θ denote the second largest or smallest eigenvalue
of Γ, and let σ0,σ1,…,σ
d
denote the associated cosine sequence. We obtain an inequality involving σ0,σ1,…,σ
d
for each integer i (1≤i≤d−1), and we show equality for all i is closely related to Γ being Q-polynomial with respect to θ. We use this idea to investigate the Q-polynomial structures in tight distance-regular graphs.
Received: January 30, 1998 Final version received: August 14, 1998 相似文献
113.
AbstractA small series of amino oligo-phenylenevinylenes (OPVs) were successfully synthesized from their nitro-analogs in a rapid, simple, and highly efficient fashion employing a sodium sulfide/pyridine system as a reducing agent. In this research, classic and sustainable reduction methodologies including NH4HCO2/Zn and a choline chloride/tin (II) chloride deep eutectic solvent (DES) were also evaluated, showing degradation products, incomplete reactivity, and product isolation difficulties in all cases. The straightforward Na2S/pyridine synthetic protocol proved to maintain the E-E stereochemistry of the OPV backbone that has been previously assembled by the Mizoroki–Heck cross-coupling reaction. Also, the optoelectronic properties were determined and discussed, considering the amino group insertion in these conjugated systems as a contribution for future construction of novel materials with applications in supramolecular electronics, light harvesting, and photocatalysis. 相似文献
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116.
We introduce affine and linearly invariant families of locally injective harmonic mappings of the unit disk . We derive sharp distortion theorems for the Jacobian that are used to establish a uniform modulus of continuity for the quasiconformal mappings in each class. Finally, we find a converse of a recent theorem of Chen and Ponnusamy characterizing when the image under a quasiconformal harmonic univalent mapping is a John domain. 相似文献
117.
118.
Analysis of cerebrospinal fluid γ‐aminobutyric acid by capillary electrophoresis with laser‐induced fluorescence detection
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Mercedes Casado Marta Molero Cristina Sierra Angels García‐Cazorla Aida Ormazabal Rafael Artuch 《Electrophoresis》2014,35(8):1181-1187
The measurement of γ‐aminobutyric acid (GABA) is suitable for investigating various neurological disorders. In this study, a sensitive and selective method for free GABA quantification in cerebrospinal fluid (CSF) has been standardised. This method is based on CE with LIF detection using 4‐fluoro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐F) as a derivatisating agent. The reaction conditions (NBD‐F concentration, pH, temperature and reaction time) and the electrophoretic parameters (run buffer composition and pH and separation voltage) were optimised to obtain the maximum derivatisation efficiency and electrophoretic resolution. The best resolution was obtained using 200 mM sodium borate, 10 mM SDS, 8.5 mM β‐CD, pH 10 and 20 kV voltage. The method was linear in the concentration range of 2.5–1000 nM with good inter‐ and intra‐assay precision values. The effects of CSF handling on free GABA concentrations were also evaluated. Our results show that the time delay between CSF collection and freezing strongly increases the CSF GABA values. Age‐related reference values were established in 55 paediatric controls. The influence of antiepileptic therapy on free CSF GABA was studied in 38 neuropaediatric patients. Significantly, higher GABA values were obtained in patients taking valproic acid or vigabatrin therapy, which are antiepileptic drugs that modulate GABA metabolism. 相似文献
119.
Muñoz-Úbeda M Misra SK Barrán-Berdón AL Aicart-Ramos C Sierra MB Biswas J Kondaiah P Junquera E Bhattacharya S Aicart E 《Journal of the American Chemical Society》2011,133(45):18014-18017
The most important objective of the present study was to explain why cationic lipid (CL)-mediated delivery of plasmid DNA (pDNA) is better than that of linear DNA in gene therapy, a question that, until now, has remained unanswered. Herein for the first time we experimentally show that for different types of CLs, pDNA, in contrast to linear DNA, is compacted with a large amount of its counterions, yielding a lower effective negative charge. This feature has been confirmed through a number of physicochemical and biochemical investigations. This is significant for both in vitro and in vivo transfection studies. For an effective DNA transfection, the lower the amount of the CL, the lower is the cytotoxicity. The study also points out that it is absolutely necessary to consider both effective charge ratios between CL and pDNA and effective pDNA charges, which can be determined from physicochemical experiments. 相似文献
120.
On the Use of Metal Purine Derivatives (M=Ir,Rh) for the Selective Labeling of Nucleosides and Nucleotides
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Marta Valencia Mamen Martín‐Ortiz Prof. Dr. Mar Gómez‐Gallego Prof. Dr. Carmen Ramírez de Arellano Prof. Dr. Miguel A. Sierra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3831-3838
The reactions of neutral or cationic IrIII and RhIII derivatives of phenyl purine nucleobases with unsymmetrical alkynes produce new metallacycles in a predictable manner, which allows for the incorporation of either photoactive (anthracene or pyrene) or electroactive (ferrocene) labels in the nucleotide or nucleoside moiety. The reported methodology (metalation of the purine derivative and subsequent marker insertion) could be used for the postfunctionalization and unambiguous labeling of oligonucleotides. 相似文献