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A series of benzylideneanilines bearing terminal polyether chains, HL (HL = R-C6H4-CHN-C6H4-R′: R = OC8H17, R′ = O(CH2CH2O)2C2H5; R = O(CH2CH2O)2C2H5, R′ = OC8H17; R = R′ = O(CH2CH2O)2C2H5; R = OC12H25, R′ = O(CH2CH2O)3C2H5; R = O(CH2CH2O)3C2H5, R′ = OC12H25; R = R′ = O(CH2CH2O)3C2H5) have been prepared. Their dinuclear, [Pd(μ-X)L]2 (X = OAc, Cl, Br, SC8), [Pd2(μ-SCn)(μ-X)L2] (X = OAc, Cl; n = 8, 2) and mononuclear orthopalladated derivatives, Pd(acac)L, Pd(Ala)L, are reported and their mesogenic properties are compared with those of the analogous compounds with alkoxy chains. In general a great lowering in the melting points is produced for all the products. The free ligands and the alanine complexes are not liquid crystals. The chloro-bridged complexes bearing alkoxy and short polyether chains (O(CH2CH2O)2C2H5) show the larger improvement of mesogenic properties. Longer polyether chains (O(CH2CH2O)3C2H5) result usually in a destabilization of the mesophases. If only polyether chains are present, the destabilization is important regardless of the chain length. The ability of these molecules as ionic extractants and transporters was qualitatively evaluated for the more propitious cis-dinuclear complexes, which in fact showed some extracting ability, modest but improved compared to the free ligands. 相似文献
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Cabalín LM Romero D García CC Baena JM Laserna JJ 《Analytical and bioanalytical chemistry》2002,372(2):352-359
A pulsed Nd:YAG laser operating on the fourth (266 nm) and second (532 nm) harmonics has been used to generate plasmas on the target surface in air at atmospheric pressure. The influence of wavelength on quantitative analysis of 4 minor elements in stainless steel samples (Si, Ti, Nb and Mo) was investigated. Stainless steel samples with different elemental concentrations were prepared and analyzed by laser-induced plasma spectrometry (LIPS). The effect of laser wavelength on analytical figures of merit (calibration curves, correlation coefficients, linear dynamic ranges, analytical precision, and accuracy values) was found to be negligible when internal standardization (an Fe line) and time-resolved laser-induced plasma are employed. For both wavelengths, the calibration curves presented a good linearity and an acceptable linear dynamic range in the concentration interval investigated. For the four elements studied, limits of detection lower than 150 microg g(-1) were achieved. To evaluate the influence of wavelength on precision and accuracy, a set of fifteen high-alloyed steel samples from different stages of steelmaking process have been analyzed. Finally, the long-term stability of the analytical measurements for Mo with 532 nm wavelength has been discussed. RSD values were lower than 5.3% for the elements studied. 相似文献
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Surowiec I Baena JR Frank J Laurell T Nilsson J Trojanowicz M Lendl B 《Journal of chromatography. A》2005,1080(2):132-139
A flow-through microdispenser has been coupled to a micro HPLC separation system and used as a solvent elimination interface for Fourier transform infrared (FTIR) and Raman spectroscopic detection of the separated compounds. Using the microdispenser picoliter sized droplets can be generated and deposited on an appropriate target placed on a computerized x, y-stage. Evaporation of volatile solvent and buffer is rapid and allows analysis of the obtained dry deposits by various techniques. Due to the destruction free character of Raman and FTIR spectroscopy they can be applied sequentially to interrogate the same deposit. In the reported application five phenolic acids typically present in wine have been separated on a C-18 column technique using a mixture of water, methanol and acetic acid as mobile phase. For spectrum acquisition infrared and Raman microscopes have been used. The spectra recorded from the dried deposits of the separated compounds agreed well with the reference spectra of corresponding components. 相似文献
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Ignacio Baena Pedro Prez-Fernndez Manuela Rodríguez-Gallardo Jos Miguel Arias 《Entropy (Basel, Switzerland)》2022,24(1)
A quantum phase transition (QPT) in a simple model that describes the coexistence of atoms and diatomic molecules is studied. The model, which is briefly discussed, presents a second-order ground state phase transition in the thermodynamic (or large particle number) limit, changing from a molecular condensate in one phase to an equilibrium of diatomic molecules–atoms in coexistence in the other one. The usual markers for this phase transition are the ground state energy and the expected value of the number of atoms (alternatively, the number of molecules) in the ground state. In this work, other markers for the QPT, such as the inverse participation ratio (IPR), and particularly, the Rényi entropy, are analyzed and proposed as QPT markers. Both magnitudes present abrupt changes at the critical point of the QPT. 相似文献
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The feasibility pump (FP) has proved to be a successful heuristic for finding feasible solutions of mixed integer linear problems. Briefly, FP alternates between two sequences of points: one of feasible solutions for the relaxed problem, and another of integer points. This short paper extends FP, such that the integer point is obtained by rounding a point on the (feasible) segment between the computed feasible point and the analytic center for the relaxed linear problem. 相似文献
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L. M. Cabalín D. Romero J. M. Baena J. J. Laserna 《Analytical and bioanalytical chemistry》1999,365(5):404-408
A pulsed Nd?:?YAG laser was used to generate a plasma from stainless steel targets in air at atmospheric pressure. Laser focusing was found to be an important factor in the ablation process. The influence of focal conditions on spatial profiles of plasma, emission intensity and averaged ablation rate (AAR, μm pulse–1) of stainless steel samples as a function of laser energy are discussed. At high energies and depending on laser beam focusing, ablation efficiency tends to decrease compared to that at lower energies. This effect can be due to plasma shielding and air breakdown. The averaged ablation rate was found to be dependent on the thickness of the sample. This effect results in shielding of the incoming laser beam and redeposition of removed material in the crater. By focusing the beam inside the material free expansion of plasma is allowed, resulting in more efficient erosion of the sample at larger energies. For comparative purposes, data on ablated mass per pulse are presented. 相似文献
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A horizontal diamond attenuated total reflection (ATR) element has been incorporated in a flow-through cell with low dead volume and used for on-line mid-IR detection in high-performance liquid chromatography. The chemical inertness of the ATR element permitted the use of a strongly acidic mobile phase in the isocratic separation. The hyphenation was used for the analysis of organic acids, sugars and alcohols in red wine. In the case of co-eluting analytes multivariate curve resolution-alternating least squares (MCR-ALS) was successfully employed for quantitative analysis. 相似文献
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L. M. Cabalín D. Romero J. M. Baena J. J. Laserna 《Fresenius' Journal of Analytical Chemistry》1999,365(5):404-408
A pulsed Nd : YAG laser was used to generate a plasma from stainless steel targets in air at atmospheric pressure. Laser
focusing was found to be an important factor in the ablation process. The influence of focal conditions on spatial profiles
of plasma, emission intensity and averaged ablation rate (AAR, μm pulse–1) of stainless steel samples as a function of laser energy are discussed. At high energies and depending on laser beam focusing,
ablation efficiency tends to decrease compared to that at lower energies. This effect can be due to plasma shielding and air
breakdown. The averaged ablation rate was found to be dependent on the thickness of the sample. This effect results in shielding
of the incoming laser beam and redeposition of removed material in the crater. By focusing the beam inside the material free
expansion of plasma is allowed, resulting in more efficient erosion of the sample at larger energies. For comparative purposes,
data on ablated mass per pulse are presented.
Received: 25 January 1999 / Revised: 7 April 1999 / Accepted: 30 April 1999 相似文献