Maximal determinant over a certain class of matrices and its application to D-optimality of designs

It is known that some optimality criteria of experimental designs are functionals of the eigenvalues of their information matrices. In this context we study the problem of maximizing the determinant of $\alpha {\mathbf{I}}_t-(\mathbf{P}+{\mathbf{P}}^T)$, $\alpha >2$, over the class of t-by-t permutation matrices, and the determinant of $\alpha {\mathbf{I}}_t+\mathbf{P}+{\mathbf{P}}^T$, $\alpha \ge 2.5$, over the class of t-by-t permutation matrices with zero diagonal (derangement matrices). The results are used to characterize D-optimal complete block designs under an interference model.     

Influence of the Hofmeister anions on self-organization of 1-decyl-3-methylimidazolium chloride in aqueous solutions

Inorganic salts usually influence water structure affecting the hydration of the molecules which lead to a salting-in or a salting-out effect of hydrophobic compounds. Specific conductivity and isothermal titration calorimetry have been used to study the effect of inorganic salts on aggregation of the cationic surfactant 1-decyl-3-methylimidazolium chloride in aqueous solutions. The effect of the concentration, the nature of the anion and temperature on micelle formation were studied. A decreasing critical micelle concentration (CMC) due to the weakening electrostatic repulsion between the headgroups was observed. The salts used in this investigation decreased the CMC and degree of micelle ionization in the order of Cl(-)相似文献   

Application of ultra-performance columns in high-performance liquid chromatography for determination of albendazole and its metabolites in turkeys

Methods for determination of albendazole (ALB), albendazole sulfoxide (SOX) and albendazole sulfone (SON) in turkey blood plasma, using high‐performance liquid chromatography (HPLC) with fluorescence detection, were developed. Moreover, comparison of HPLC columns with ultra‐performance liquid chromatography (UPLC) columns was performed. Albendazol was administered orally in 5‐week‐old birds (n = 18) at a dose of 25 mg/kg b.w. Accuracy and precision of the developed method were satisfactory and stability studies showed acceptable variation (below 15%) in ALB, SOX and SON concentrations when the samples were stored at –75°C for 15 days. UPLC® columns gave higher peaks from typical HPLC columns retaining high quality of analysis. Pharmacokinetic analysis indicated quick elimination of ALB from turkey blood plasma. The mean residence time of SON was at least two times longer than that of SOX and four times longer than that of ALB. The elimination half‐lives for ALB, SOX and SON were 0.7 ± 0.27, 5.37 ± 6.03, 9.17 ± 5.12 h, respectively. The obtained results indicate that the described method allows for precise determination of albendazole and its metabolites in turkey plasma. Moreover, using UPLC columns in HPLC apparatus results in higher sensitivity as compared with the classical HPLC columns. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparative model studies of gastric toxicity of nonsteroidal anti-inflammatory drugs

A high percentage of people treated with a long-term nonsteroidal anti-inflammatory drug (NSAID) therapy suffer NSAID-induced gastrointestinal-tract-related side effects. A current hypothesis states that the side effects are related to the topical action of NSAID molecules on gastric mucus that lowers its resistance to luminal acid. The main lipids in human mucus are palmitoyloleoylphosphatidylcholine (POPC) and cholesterol (Chol). In this study, both X-ray diffraction and molecular dynamics (MD) simulation methods were employed to investigate the effects of selected NSAIDs in protonated and deprotonated states on the structural parameters of a POPC-Chol bilayer. The drugs were three commonly used NSAIDs with apparently different gastric toxicity: ketoprofen (KET), aspirin (ASP), and piroxicam (PXM). Both methods revealed that the effects of the NSAIDs on the POPC-Chol bilayer parameters were moderate and only slightly differentiated among the drugs. Much larger differences among the drugs were noticed in their interactions with interfacial water and Na(+) as well as with the polar groups of POPC and Chol, mainly via H-bonds. Of the three NSAIDs, KET interacted with POPC and water the most extensively, whereas ASP interacted with Chol and Na(+) more than did the other two. Interactions of PXM with POPC and Chol polar groups as well as with water and Na(+) were limited.     

Remnant fermi surfaces in photoemission

Recent experiments have introduced a new concept for analyzing the photoemission spectra of correlated electrons-the remnant Fermi surface (rFs), which can be measured even in systems which lack a conventional Fermi surface. Here, we analyze the rFs in a number of interacting electron models, and find that the results fall into two classes. For systems with particle-particle (pairing) instabilities, the rFs is an accurate replica of the true Fermi surface. In the presence of particle-hole (nesting) instabilities, the rFs is a map of the resulting superlattice Brillouin zone. The results suggest that the gap in Ca2CuO2Cl2 is of particle-hole origin.     

Coordination behaviour and thermolysis of some rare-earth complexes with 4,4′-bipyridine and di- or trichloroacetates

A novel mixed-ligand complexes with empirical formulae: Dy(4-bpy)(CCl₂HCOO)₃ · H₂O and Ln(4-bpy)_1.5(CCl₃COO)₃ · 2H₂O (where Ln(III) = Ce, Nd) were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulfoxide). Analysis of the diffractograms showed that the obtained complexes are crystalline. Way of metal-ligand coordination discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Ln₂O₃ (Nd, Dy) and CeO₂. TG-MS system was used to analyse principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Dy(4-bpy)(CCl₂HCOO)₃ · H₂O in air.     

Intermediate coupling model of cuprates: Adding fluctuations to a weak coupling model of pseudogap and superconductivity competition

We demonstrate that many features ascribed to strong correlation effects in various spectroscopies of the cuprates are captured by a calculation of the self-energy incorporating effects of spin and charge fluctuations. The self-energy is calculated over the full doping range from half-filling to the overdoped system. In the normal state, the spectral function reveals four subbands: two widely split incoherent bands representing the remnant of the two Hubbard bands, and two additional coherent, spin- and charge-dressed in-gap bands split by a spin-density wave, which collapses in the overdoped regime. The resulting coherent subbands closely resemble our earlier mean-field results. Here we present an overview of the combined results of our mean-field calculations and the newer extensions into the intermediate coupling regime.     

What is the best DFT functional for vibronic calculations? A comparison of the calculated vibronic structure of the S1-S0 transition of phenylacetylene with cavity ringdown band intensities

The sensitivity of vibronic calculations to electronic structure methods and basis sets is explored and compared to accurate relative intensities of the vibrational bands of phenylacetylene in the S(1)(A(1)B(2)) ← S(0)(X(1)A(1)) transition. To provide a better measure of vibrational band intensities, the spectrum was recorded by cavity ringdown absorption spectroscopy up to energies of 2000 cm(-1) above the band origin in a slit jet sample. The sample rotational temperature was estimated to be about 30 K, but the vibrational temperature was higher, permitting the assignment of many vibrational hot bands. The vibronic structure of the electronic transition was simulated using a combination of time-dependent density functional theory (TD-DFT) electronic structure codes, Franck-Condon integral calculations, and a second-order vibronic model developed previously [Johnson, P. M.; Xu, H. F.; Sears, T. J. J. Chem. Phys. 2006, 125, 164331]. The density functional theory (DFT) functionals B3LYP, CAM-B3LYP, and LC-BLYP were explored. The long-range-corrected functionals, CAM-B3LYP and LC-BLYP, produced better values for the equilibrium geometry transition moment, but overemphasized the vibronic coupling for some normal modes, while B3LYP provided better-balanced vibronic coupling but a poor equilibrium transition moment. Enlarging the basis set made very little difference. The cavity ringdown measurements show that earlier intensities derived from resonance-enhanced multiphoton ionization (REMPI) spectra have relative intensity errors.