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In this paper, three new direct Mutually Orthogonal Latin Squares (MOLS) constructions are presented for 7 MOLS(24), 7 MOLS(75) and 8 MOLS(36); then using recursive methods, several new constructions for 7 and 8 MOLS are obtained. These reduce the largest value for which 7 MOLS are unknown from 780 to 570, and the largest odd value for which 8 MOLS are unknown from 1935 to 419. © 2003 Wiley Periodicals, Inc. 相似文献
3.
4.
Rastislav Varga Arcady Zhukov Michail Ipatov Juan Maria Blanco Julian Gonzalez Valentina Zhukova Pavol Vojtanik 《Journal of magnetism and magnetic materials》2006
The effect of the glass coating on the single domain wall potential in amorphous glass-coated Fe-based microwire has been studied by the switching field distribution technique. The thermoactivated mechanism model is used to describe the thermally activated switching through the complex energy barrier in amorphous FeSiB microwires. Glass removal leads to the increase of the probability of the thermally activated switching pointing to the decrease of the energy barrier. 相似文献
5.
Héctor Beltrán Nahum Masó Beatriz Julian Eloisa Cordoncillo Juan B. Carda Purificación Escribano Anthony R. West 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1061-1065
Lead Magnesium Niobate, Pb(Mg1/3Nb2/3)O3 (PMN), is an important relaxor ferroelectric material. A significant problem exists, however, in the preparation of this material: it is very difficult to prepare pure phase, without the presence of a pyrochlore impurity phase which degrades the dielectric properties. Depending on the processing conditions, the amount of pyrochlore phase varies.Considering the ternary diagram PbO-MgO-Nb2O5, different compositions have been prepared by a simple sol-gel method at room temperature using Pb(CH3COO)2, Mg(CH3COO)2, Nb(OC2H5)5 as precursors. After the heat treatment, the samples obtained were analyzed by XRD and EPMA with the purpose of studying the compositions formed.From the analysis of these results, it seems to be that the appearance of pyrochlore can be related to the reactivity of the MgO and/or the presence of other phases of the binary system PbO-Nb2O5. An excess of Pb and Mg is necessary for compositions to be formed near the PMN. The control of the amount of these two elements is very important because an excess of MgO would lead to rich compositions in Mg as a secondary phase. 相似文献
6.
Chirality control in optically active polysilane aggregates 总被引:1,自引:0,他引:1
A novel strategy for controlling the higher order chirality of aggregates prepared from enantiopure polysilanes is experimentally probed and discussed. Structurally similar poly[n-alkyl(aryl)]silanes were synthesized in which one side chain comprised the chiral (S)-2-methylbutyl group and the other an achiral m- or p-alkyl-substituted phenyl ring. In solution the polymers adopt helical conformations with the same induced preferential screw sense chirality, as evidenced by circular dichroism (CD) spectroscopy. Aggregates, however, formed by addition of a nonsolvent to a polymer solution, show oppositely signed CD spectra. Consistent results were obtained for another series of poly[p-n-alkyl(aryl)]silanes where alkyl is butyl, propyl, and ethyl. The sense of the aggregate higher order chirality is dependent on the chemical composition and environment and is coarse-tunable by adjusting the length of the achiral side chain and fine-tunable by adjusting the good/poor solvent ratio. The origin of these effects is discussed with reference to a simple model. 相似文献
7.
Laurent Chaloin Nicole Van Mau Frédéric Heitz Laurent Chiche Jean-Claude Talbot 《Colloids and surfaces. B, Biointerfaces》1998,10(6):389R-412
In order to elucidate the influence on the lipidic environment on the recognition process of its membrane associated receptor, the interactions of the vasoconstrictor peptide endothelin 1 with various phospholipids have been investigated using different lipidic model membranes: monolayers at constant surface pressure, vesicles and micelles. A monolayer study of ET1 adsorbed onto the water surface has shown that the C-terminus of the peptide points towards the aqueous phase. Penetration measurements into lipidic monolayers indicate that ET1 adsorbs to phospholipids with an orientation similar to that of the air–water interface and fluorescence measurements are in agreement with such an orientation of the peptide. This adsorption is selective for neutral phospholipids and indicates that the nature of the phospholipid headgroups is of major importance for the approach of the membrane associated receptor. 相似文献
8.
Simon Doherty Julian G. Knight Tom H. Scanlan Mark R. J. Elsegood William Clegg 《Journal of organometallic chemistry》2002,650(1-2):231-248
The aprotic and protic bi- and multidentate iminophosphines 2-Ph2PC6H4N=CR1R2 (R1=H, R2=Ph=2a; R1=Me R2=Ph=2b; R1=H, R2=2-thienyl=2c; R1=H, R2=C6H4-2-PPh2=2d; R1=H, R2=C6H4-2-OH=2e, R1=H, R2=C6H4-2-OH-3-But=2f; R1=H, R2=CH2C(O)Me=2g) have been prepared by the acid catalyzed condensation of 2-(diphenylphosphino)aniline with the corresponding aldehyde–ketone. Iminophosphine 2d can be reduced with sodium cyanoborohydride to give the corresponding amino-diphosphine 2-Ph2PC6H4N(H)CH2C6H4-2-PPh2 (2h). In the presence of a stoichiometric quantity of acid, 2-(diphenylphosphino)aniline reacts in an unexpected manner with benzaldehyde, salicylaldehyde, or acetophenone to give the corresponding 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and with pyridine-2-carboxaldehyde to give N-(pyridin-2-ylmethyl)-2-diphenylphosphinoylaniline, the latter of which has been characterized by single-crystal X-ray crystallography, as its palladium dichloride derivative. The attempted condensation of 2-(diphenylphosphino)aniline with pyridine-2-carboxaldehyde to give the corresponding pyridine-functionalized iminophosphine resulted in an unusual transformation involving the diastereoselective addition of two equivalents of aldehyde to give 1,2-dipyridin-2-yl-2-(o-diphenylphosphinoyl)phenylamino-ethanol, which has been characterized by a single-crystal X-ray structure determination. The bidentate iminophosphine 2-Ph2PC6H4N=C(H)Ph reacts with [(cycloocta-1,5-diene)PdClX] X=Cl, Me) to give [Pd{2-Ph2PC6H4N=C(H)Ph}ClX] and the imino-diphosphine 2-Ph2PC6H4N=C(H)C6H4-PPh2 reacts with [(cycloocta-1,5-diene)PdClMe] to give [Pd{2-Ph2PC6H4N=C(H)C6H4---PPh2}ClMe] and each has been characterized by single-crystal X-ray crystallography. The monobasic iminophosphine 2-Ph2PC6H4N=C(Me)CH2C(O)Me reacts with [Ni(PPh3)2Cl2] in the presence of NaH to give the phosphino–ketoiminate complex [Ni{2-Ph2PC6H4N=C(Me)CHC(O)Me}Cl], which has been structurally characterized. Mixtures of iminophosphines 2a–h and a palladium source catalyze the Suzuki cross coupling of 4-bromoacetophenone with phenyl boronic acid. The efficiency of these catalysts show a marked dependence on the palladium source, catalysts formed from [Pd2(OAc)6] giving consistently higher conversions than those formed from [Pd2(dba)3] and [PdCl2(MeCN)2]. Catalysts formed from neutral bi- and terdentate iminophosphines 2a–d gave significantly higher conversions than those formed from their monobasic counterparts 2e–f. Notably, under our conditions the conversions obtained with 2a–c compare favorably with those of the standards; catalysts formed from tris(2-tolyl)phosphine and tris(2,4-di-tert-butylphenyl)phosphite and a source of palladium. In addition, mixtures of [Ir(COD)Cl]2 and 2a–h are active for the hydrosilylation of acetophenone; in this case catalysts formed from monobasic iminophosphines 2e–f giving the highest conversions. 相似文献
9.
Precise conductance measurements are reported on dilute aqueous solutions of the sodium and potassium salts of orthophosphoric
acid at 25 ∘C. Conductance measurements on solutions of electrolytes such as these phosphate salts that exist in solution as complicated
mixtures of ions have previously proved difficult to interpret. To overcome this, a mathematical method has been developed
to calculate the concentrations of all the species in the aqueous system M3PO4/M2HPO4/M2HPO4/H3PO4 (M = Na or K) over a continuous range of stoichiometries. The Lee–Wheaton conductance equation has been used to interpret
the conductance of these multicomponent solutions in terms of the limiting ionic conductances and concentrations of all the
ions in the solution. The limiting molar conductances of the ions H2PO4
− and HPO4
2− and the ion-pair formation constants of these ions with sodium and potassium ions were determine
This work has enabled the accurate determination of solution parameters for the important hydrogenphosphate ions in water
and provides an excellent example of the use of an advanced conductance theory in the analysis of the conductance of multicomponent
electrolyte systems. 相似文献
10.
Meyer M Bée A Talbot D Cabuil V Boyer JM Répetti B Garrigos R 《Journal of colloid and interface science》2004,277(2):309-315
Synthesis of nanometric platelet-like Ni(OH)2 particles is described. The role of several experimental parameters on the particle size is investigated. A colloidal dispersion of particles is produced by adsorbing ionizable organic ligands (trisodium citrate) on the particle surface. The stability of this colloidal dispersion and the particle charge density are determined for different citrate ions concentrations. 相似文献