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81.
Anthony H. Jackson K. R. Nagaraja Rao N. Sim Ooi Esther Adelakun 《Tetrahedron letters》1984,25(52):6049-6050
Treatment of α-methylpyrroles with thallium (III) nitrate/Montmorillonite clay affords the corresponding α-formylpyrroles in excellent yields. 相似文献
82.
This study investigates two sixth grade students’ dilemmas regarding the parity of zero. Both students originally claimed that zero was neither even nor odd. Interviews revealed a conflict between students’ formal definitions of even numbers and their concept images of even numbers, zero, and division. These images were supported by practically based explanations relying on everyday contexts. By using mathematically based explanations that rely solely on mathematical notions, students were able to correctly conclude that zero is an even number. Extending the natural number system in elementary school to include zero can be used as springboard to encourage the use of mathematically based explanations. 相似文献
83.
84.
Esther Domínguez Concepción Laborra Aranzazu Linaza Ana Madoz Issa A. Katime 《Monatshefte für Chemie / Chemical Monthly》1989,120(8-9):743-748
Summary A series of mono and diesters of itaconic acid containing alkoxy and sulfide side chains of variable lengths has been synthesized. Their structures have been established on the basis of their spectral data.
Eine Serie von Mono- und Diestern von Itaconsäure: Synthese und Strukturbestimmung
Zusammenfassung Es wurde eine Serie von Mono- und Diestern von Itaconsäure mit Alkoxy- und Sulfidseitenketten variabler Länge synthetisiert. Die Strukturaufklärung erfolgte mittels spektroskopischer Daten.相似文献
85.
Correa A Tellitu I Domínguez E Moreno I Sanmartin R 《The Journal of organic chemistry》2005,70(6):2256-2264
[reaction: see text] The synthesis of a series of optically pure benzo-, naphtho-, and heterocycle-fused pyrrolo[2,1-c][1,4]-diazepin-5,11-dione derivatives starting from l-proline methyl ester is presented. The synthetic plan includes an aroylation step at the proline nitrogen followed by transformation of the ester residue into a N-methoxyamide group. The subsequent key cyclization step embraces the PIFA mediated formation of a N-acylnitrenium intermediate and its succeeding intramolecular trapping by the aromatic ring. The presented general approach solves the need of starting from not very accessible amino (or a related functionality) aromatic starting materials, and its effectiveness is demonstrated in the synthesis of the antitumor antibiotic DC-81. 相似文献
86.
Quintanilla E Dávalos JZ Abboud JL Alcamí M Cabildo MP Claramunt RM Elguero J Mó O Yáñez M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(6):1826-1832
Fourier transform ion cyclotron resonance spectroscopy (FT ICR) techniques, including collision-induced dissociation (CID) methodology, were applied to the study of the gas-phase protonation of pivalaldehyde (1) and 1-adamantanecarbaldehyde (2). A new synthetic method for 2 was developed. The experiments, together with a thorough computational study involving ab initio and density functional theory (DFT) calculations of high level, conclusively show that upon monoprotonation in the gas phase, compound 1 yields monoprotonated methyl isopropyl ketone 3. The mechanism of this gas-phase acid-catalyzed isomerization is different from that reported by Olah and Suryah Prakash for the reaction in solution. In the latter case, isomerization takes place through the diprotonation of 1. 相似文献
87.
A method of sum composition for construction of orthogona Latin squares was introduced by A. Hedayat and E. Seiden [1]. In this paper we exhibit procedures for constructing a pair of orthogonal Latin squares of size pα + 4 for primes of the form 4m + 1 or p ≡ 1, 2, 4 mod 7. We also show that for any p > 2n and n even one can construct and orthogonal pair of Latin squares of size pα + n using the method of sum composition. We observe that the restriction xy = 1 used by Hedayat and Seiden is sometimes necessary. 相似文献
88.
Santos Blanco Francisco J Molina Lourdes Castro Maria L Del Moral Raquel Hernandez Ana Jimenez Alma Rus Esther Martinez-Lara Eva Siles Maria A Peinado 《BMC neuroscience》2010,11(1):78
Background
The cerebellum is the neural structure with the highest levels of nitric oxide, a neurotransmitter that has been proposed to play a key role in the brain aging, although knowledge concerning its contribution to cerebellar senescence is still unclear, due mainly to absence of integrative studies that jointly evaluate the main factors involved in its cell production and function. Consequently, in the present study, we investigate the expression, location, and activity of nitric oxide synthase isoenzymes; the protein nitration; and the production of nitric oxide in the cerebellum of adult and old rats. 相似文献89.
Esther Beneish 《Proceedings of the American Mathematical Society》2006,134(7):1869-1873
Let be a prime greater than , and let be the semi-direct product of a group of order by a cyclic group of order , which acts faithfully on . Let be the localization of at . We show that the Krull-Schmidt Theorem fails for the category of invertible -lattices.
90.
A rapid method has been developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in soil based on their sonication-assisted extraction in small columns (SAESC) with a low volume of ethyl acetate and subsequent quantitation and identification by GC with electron impact mass spectrometric detection in the SIM mode (GC-MS-SIM). Spiked blank soil extracts were used as standards to counteract the matrix effect observed in the chromatographic determination. PAHs were confirmed at trace level by their retention times, their qualifier and target ions, and their qualifier/target abundance ratios. Recovery studies were performed at 0.5, 1.0, 5.0, and 10 microg/kg fortification levels for each PAH, and the recoveries obtained ranged from 91.2 to 99.8% with RSDs between 0.4 and 9.3%. The detection limits of the method ranged from 0.03 to 0.3 microg/kg for the different PAHs studied. The developed method is linear over the range assayed, 1-100 microg/L with determination coefficients higher than 0.996. PAH levels were determined using this method in soil samples taken from different agricultural areas of Spain. In general, PAH concentrations were low and the most frequently occurring PAHs were naphthalene, pyrene, phenanthrene, and fluoranthene. 相似文献