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41.
Nihan Nugay Gabor Erdodi J. P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》2005,43(3):630-637
This article mainly concerns the synthesis of novel PD5/PDMS conetworks by the copolymerization of cyclic D5H and linear HO? PDMS? OH units, and the characterization of the product by DMTA, DSC, and TGA. The ultimate properties of the conetworks may be controlled by varying the relative composition of D5H and PDMS components. DMTA and DSC thermograms indicate compatibility between the PD5 and PDMS domains. Understanding of the polymer chemical transformations involved in conetwork formation combined with an analysis of DMTA and DSC thermograms led to a proposition of the microarchitecture of PD5/PDMS conetworks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 630–637, 2005 相似文献
42.
Synthesis and pH‐Dependent Spectroscopic Behavior of 2,4,6‐Trisubstituted Pyridine Derivatives 下载免费PDF全文
Gala Chapman Isaac Solomon Gabor Patonay Maged Henary 《Journal of heterocyclic chemistry》2015,52(3):861-872
Seven 2,4,6‐trisubstituted pyridine derivatives with N,N‐diethylaniline substituents at the 4‐position were synthesized, and their spectroscopic properties in the absence and presence of acid were studied. The spectral effects of protonation, molar absorptivities, pKa values, and the structural origins of the observed spectral behavior were ascertained. The pyridine nitrogen was found to be more basic than the diethylamino nitrogen atom. Protonation of the pyridine ring nitrogen is associated with the appearance of a red‐shifted intramolecular charge transfer peak in the UV‐visible spectra. Favorable color indicating properties result from electron‐donating substitution at the 2 and 6 positions of pyridine, which provide a greater absorptivity of the red‐shifted peak associated with protonation of the pyridine nitrogen. These findings will assist in the design and optimization of these compounds for ion‐indicating and pH‐sensing applications. 相似文献
43.
Dr. Walter T. Ralston Dr. Gérôme Melaet Tommy Saephan Prof. Gabor A. Somorjai 《Angewandte Chemie (International ed. in English)》2017,56(26):7415-7419
The Fischer–Tropsch process, or the catalytic hydrogenation of carbon monoxide (CO), produces long chain hydrocarbons and offers an alternative to the use of crude oil for chemical feedstocks. The observed size dependence of cobalt (Co) catalysts for the Fischer–Tropsch reaction was studied with colloidally prepared Co nanoparticles and a chemical transient kinetics reactor capable of measurements under non-steady-state conditions. Co nanoparticles of 4.3 nm and 9.5 nm diameters were synthesized and tested under atmospheric pressure conditions and H2/CO=2. Large differences in carbon coverage (ΘC) were observed for the two catalysts: the 4.3 nm Co catalyst has a ΘC less than one while the 9.5 nm Co catalyst supports a ΘC greater than two. The monomer units present on the surface during reaction are identified as single carbon species for both sizes of Co nanoparticles, and the major CO dissociation site is identified as the B5-B geometry. The difference in activity of Co nanoparticles was found to be a result of the structure sensitivity caused by the loss of these specific types of sites at smaller nanoparticle sizes. 相似文献
44.
Ramzia I. El-Bagary Gabor Patonay Asmaa A. Elzahr Ehab F. Elkady Walid A. Ebeid 《Chromatographia》2014,77(3-4):257-264
A rapid and precise LC method was developed for the simultaneous determination of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) using acetonitrile:25 mM octane sulfonic acid sodium salt monohydrate in water (60:40 v/v) as the mobile phase. The flow rate was maintained at 1.2 mL min?1 on a stationary phase composed of Supelco, Discovery® HS (C18) column (25 cm × 4.6 mm, 5 μm). Isocratic elution was applied throughout the analysis. Detection was carried out at λ max (232 nm) at ambient temperature. The method was validated according to ICH guidelines. Linearity, accuracy and precision were satisfactory over the concentration ranges of 32–320, 2–44 and 4–64 μg mL?1 for ALS, AML and HCZ, respectively. LOD and LOQ were estimated and found to be 0.855 and 2.951 μg mL?1, respectively, for ALS, 0.061 and 0.202 μg mL?1, respectively, for AML as well as 0.052 and 0.174 μg mL?1, respectively, for HCZ. The method was successfully applied for the determination of the three drugs in their co-formulated tablets. The results were compared statistically with reference methods and no significant difference was found. The developed method is specific and accurate for the quality control and routine analysis of the cited drugs in pharmaceutical preparations. 相似文献
45.
Hickmann V Kondoh A Gabor B Alcarazo M Fürstner A 《Journal of the American Chemical Society》2011,133(34):13471-13480
Concise and protecting-group-free total syntheses of the marine oxylipins hybridalactone (1) and three members of the ecklonialactone family (2-4) were developed. They deliver these targets in optically pure form in 14 or 13 steps, respectively, in the longest linear sequence; five of these steps are metal-catalyzed and four others are metal-mediated. The route to either 1 or 2-4 diverges from the common building block 22, which is accessible in 7 steps from 2[5H]furanone by recourse to a rhodium-catalyzed asymmetric 1,4-addition reaction controlled by the carvone-derived diene ligand 35 and a ring-closing alkene metathesis (RCM) catalyzed by the ruthenium indenylidene complex 17 as the key operations. Alternatively, 22 can be made in 10 steps from furfural via a diastereoselective three-component coupling process. The further elaboration of 22 into hybridalactone as the structurally most complex target with seven contiguous chiral centers was based upon a sequence of cyclopropanation followed by a vanadium-catalyzed epoxidation, both of which were directed by the same free hydroxy group at C15. The macrocyclic scaffold was annulated to the headgroup by means of a ring-closing alkyne metathesis reaction (RCAM). In response to the unusually high propensity of the oxirane of the targeted oxylipins for ring opening, this transformation had to be performed with complexes of the type [(Ar(3)SiO)(4)Mo≡CPh][K·OEt(2)] (43), which represent a new generation of exceedingly tolerant yet remarkably efficient catalysts. Their ancillary triarylsilanolate ligands temper the Lewis acidity of the molybdenum center but are not sufficiently nucleophilic to engage in the opening of the fragile epoxide ring. A final semireduction of the cycloalkyne formed in the RCAM step to the required (Z)-alkene completed the total synthesis of (-)-1. The fact that the route from the common fragment 22 to the ecklonialactones could follow a similar logic showcased the flexibility inherent to the chosen approach. 相似文献
46.
47.
A.F. Gabor 《Operations Research Letters》2006,34(3):257-263
We propose a 2-approximation algorithm for a facility location problem with stochastic demands. At open facilities, inventory is kept such that arriving requests find a zero inventory with (at most) some pre-specified probability. Costs incurred are expected transportation costs, facility operating costs and inventory costs. 相似文献
48.
We investigate the structure of a collineation groupG preserving an oval in a finite projective plane of odd order and we obtain several results aboutG, whenG is a2-group. These results are then used to investigate the structure ofG/O(G) in the general case and, in particular, that ofF*(G/O(G)).This research was supported in part by a grant from the M.U.R.S.T. 相似文献
49.
We study the existence of solutions to a system of two inclusions involving Fredholm operators of nonnegative (Fredholm) index
and the so-called c-admissible maps: upper semicontinuous maps with values being continuous images of cell-like sets. The presented approach
resembles the substitution technique, i.e. applies the so-called solution map. The appearance of the ‘dimension defect’ reflecting
the nonnegativity of Fredholm indices requires the use of algebraic tools based on the cohomotopy theory, different from the
usual homological ones present in the fixed point theory. An application to boundary value problems is provided as well as
the brief exposition of basic facts from the cohomotopy theory.
Mathematics Subject Classifications (2000) 47H04, 47A53, 55M20, 55Q55, 34A60. 相似文献
50.