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This article reports on an exploratory investigation of the measurement estimation performance of ten Iranian high school students on a set of real-world length and area measurement tasks. The results of a qualitative analysis of the data indicate that the students employed a variety of either mental or physically present Individual Frames of Reference as the non-tool units of measure in various estimation tasks. The analysis also found that a range of types of frames of reference was used across students in response to particular tasks and to the physical environments in which the tasks were situated. These results suggest that there is a complex interaction among a student’s individual preference for a particular type of Individual Frame of Reference, the nature of the estimation activity, and the physical context in which the activity takes place. These findings, which contribute to an understanding of the nature of the measurement unit that is employed during an estimation process, provide a different perspective from other studies that focus on categorizing estimation strategies, or processes. 相似文献
33.
Murat Aydemir Akın Baysal Nevin Gürbüz İsmail Özdemir Bahattin Gümgüm Saim Özkar Nagihan Çaylak Leyla Tatar Yıldırım 《应用有机金属化学》2010,24(1):17-24
Three new (N‐diphenylphosphino)‐isopropylanilines, having isopropyl substituent at the carbon 2‐ (1) 4‐ (2) or 2,6‐ (3) were prepared from the aminolysis of chlorodiphenylphosphine with 2‐isopropylaniline, 4‐isopropylaniline or 2,6‐diisopropylaniline, respectively, under anaerobic conditions. Oxidation of 1,2 and 3 with aqueous hydrogen peroxide, elemental sulfur or gray selenium gave the corresponding oxides, sulfides and selenides (Ph2P?E)NH? C6H4? 2‐CH(CH3)2, (Ph2P?E)NH? C6H4? 4‐CH(CH3)2 and (Ph2P?E)NH? C6H4? 2,6‐{CH(CH3)2}2, where E = O, S, or Se, respectively. The reaction of [M(cod)Cl2] (M = Pd, Pt; cod = 1,5‐cyclooctadiene) with two equivalents of 1,2 or 3 yields the corresponding monodendate complexes [M((Ph2P)NH? C6H4? 2‐CH(CH3)2)2Cl2], M = Pd 1d, M = Pt 1e, [M((Ph2P)NH? C6H4? 4‐CH(CH3)2)2Cl2], M = Pd 2d, M = Pt 2e and [M((Ph2P)NH? C6H4? 2,6‐(CH(CH3)2)2)2Cl2], M = Pd 3d, M = Pt 3e, respectively. All the compounds were isolated as analytically pure substances and characterized by NMR, IR spectroscopy and elemental analysis. Furthermore, representative solid‐state structure of [(Ph2P?S)NH? C6H4? 4‐CH(CH3)2] (2b) was determined using single crystal X‐ray diffraction technique. The complexes 1d–3d were tested and found to be highly active catalysts in the Suzuki coupling and Heck reaction, affording biphenyls and stilbenes, respectively. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Leyla Gidi Jessica Honores José Ibarra María Jesús Aguirre Roxana Arce Galo Ramírez 《Electroanalysis》2022,34(7):1163-1173
In this work, the determination of gallic acid was performed using surface-renewable carbon paste electrodes fabricated with multi-walled carbon nanotubes (MWCNT) and a mixture of N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid with mineral oil (MO) as binder. This system shows remarkable amperometric sensor characteristics and promotes a better electronic transfer. An electroanalytical study of gallic acid shows a linear range from 4.98±0.25 to 74.1±2.2 μmol L−1, with R2=0.9958 and an experiment a limit of detection of 2.70±0.08 μmol L−1 (S/N=3), and a sensitivity of 0.029 μA μmol−1 L. 相似文献
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Leyla Daruis Pablo Gonzlez-Vera Francisco Marcelln 《Journal of Computational and Applied Mathematics》2002,140(1-2)
Let μ be a probability measure on [0,2π]. In this paper we shall be concerned with the estimation of integrals of the form
For this purpose we will construct quadrature formulae which are exact in a certain linear subspace of Laurent polynomials. The zeros of Szegö polynomials are chosen as nodes of the corresponding quadratures. We will study this quadrature formula in terms of error expressions and convergence, as well as, its relation with certain two-point Padé approximants for the Herglotz–Riesz transform of μ. Furthermore, a comparison with the so-called Szegö quadrature formulae is presented through some illustrative numerical examples. 相似文献
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Leyla Tatar Gülsün Gkaac Diner Ülkü 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):668-669
The title compound, [Cu(C6H2Br3O)2(NH3)2], a monomeric centrosymmetric CuII complex, crystallizes in the monoclinic system. The CuO2N2 coordination sphere is trans planar, [Cu—O 1.943 (5) Å and Cu—N 1.977 (6) Å], with the fifth and sixth coordination sites occupied by Br atoms from the phenoxide ions [Cu—Br 3.129 (1) Å], resulting in an elongated distorted octahedral structure for the CuO2N2Br2 coordination. Each of the NH3 groups forms two hydrogen bonds with the Br and O atoms of the CuO2N2Br2 moiety of a neighbouring molecule. This arrangement constitutes a one‐dimensional chain along the x axis of the unit cell. 相似文献
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Nuran Asmafiliz Zeynel Kılıç Aslı Öztürk Yasemin Süzen Tuncer Hökelek Leyla Açık 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):1723-1742
Abstract The condensation reactions of hexachlorocyclotriphosphazene (N3P3Cl6) with mono (1 and 2) and bisferrocenyldiamines (3–5 and 7) resulted in the formation of tetrachloro mono- (8 and 9) and bisferrocenylspirocyclotriphosphazenes (10–13). In addition the tetramorpholino mono- (8a and 9a) and bisferrocenylphosphazenes (10a–12a) were obtained from the reactions of the corresponding tetrachlorophosphazenes (8–12) with excess morpholine. The structures of all the phosphazenes were determined using FTIR, MS, 1H, 13C, and 31P NMR and 2-dimensional NMR techniques. The structures of 9a and 13 were determined by single crystal X-ray diffraction techniques. Cyclic voltammetric investigations of compounds 8a, 9a, and 11a revealed that ferrocene redox centers undergo reversible oxidation. These ferrocenylphosphazenes appear to be quite robust electrochemically. Interactions between the compounds 8a, 9a, 11a, and 12a and pBR322 plasmid DNA were investigated by agarose gel electrophoresis. [Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text and figures.] 相似文献
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Asaf E. Evren Leyla Yurttas Büşra Ekselli Gülşen Akalin-Ciftci 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):820-828
AbstractNew N-(5-methyl-4-phenylthiazol-2-yl)-2-(substituted thio)acetamides were synthesized and studied for their anticancer activity. The title compounds were procured by reacting 2-chloro-N-(5-methyl-4-phenylthiazol-2-yl)acetamide with some mercapto derivatives. The structural elucidation of the compounds was performed by 1H-NMR, 13C-NMR and LC-MS/MS spectral data and elemental analyses. The synthesized compounds were investigated for their antitumor activities against A549 human lung adenocarcinoma cells and NIH/3T3 mouse embryoblast cell line for determining their selective cytotoxicity. 2-[(1-methyl-1H-tetrazol-5-yl)thio]-N-(5-methyl-4-phenylthiazol-2-yl)acetamide (4c) showed high selectivity, and whose IC50 value was determined as 23.30?±?0.35?µM and >1000?µM against A549 human lung adenocarcinoma cells and NIH/3T3 mouse embryoblast cell lines, respectively. 2-[(1-Methyl-1H-imidazol-2-yl)thio]-N-(5-methyl-4-phenyl thiazol-2-yl)acetamide (4a) and 2-[(1-Methyl-1H-tetrazol-5-yl)thio]-N-(5-methyl-4-phenyl thiazol-2-yl)acetamide (4c) exhibited the highest apoptosis percentage among those tested, but not as high as the standard, cisplatin. 相似文献
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Nezire Saygılı Meral Özalp Leyla Tatar Yıldırım 《Journal of heterocyclic chemistry》2014,51(5):1264-1269
Oxazolidinethione compounds were synthesized starting from racemic and enantiopure β‐amino alcohols. The molecular structure of oxazolidinethione 6a was elucidated by single‐crystal x‐ray crystallography. Oxazolidinethione compounds screened for antimicrobial activity showed mild minimum inhibitory concentration values. 相似文献
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We have calculated relativistic energies and Landé factors for 5d6s
2, 5d
26s, 6s6p
2, 6s
27s, 5d
3, 5d6s7s, 6s
26p, 5d6s6p, 5d
26p and 6s
27p excited levels outside the core [Xe]4f
14 in neutral lutetium (Lu I, Z = 71). These calculations are based on the multiconfiguration Hartree-Fock (MCHF) method, within the framework of the Breit-Pauli
relativistic corrections. Moreover, the results obtained have been compared with other works. 相似文献