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71.
72.
Bernard?A.?BoukampEmail author Matthijs?W.?den?Otter Henny?J.?M.?Bouwmeester 《Journal of Solid State Electrochemistry》2004,8(9):592-598
The conductivity relaxation (CR) method is often used for measuring the surface transfer rate,
Ktr, and the bulk diffusion coefficient,
for oxygen transport in mixed conducting oxides (MIECs). The time domain analysis of the obtained CR response is rather complex and is based on ideal behaviour for the diffusion process. It is quite favourable to perform the data analysis in the frequency domain, where non-ideal responses are easily recognised. Besides, frequency domain analysis (impedance spectroscopy) can yield reliable parameter estimates. Using a discrete Fourier-transform procedure, the time domain responses can be transformed to a frequency domain impedance-type expression. This approach can be applied to any system for which a driving force and a resulting flux can be defined.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003 相似文献
73.
John M. Warman Matthijs P. De Haas Andries Hummel Cyril A.G.O. Varma Piet H.M. Van Zeyl 《Chemical physics letters》1982,87(1):83-86
Dipole moment changes accompanying the formantion of singlet and triplet excited states of 4-dimethylamino-4′-nitro- stilbene on laser flash photolysis of solutions in n-hexane and benzene have been observed by measuring changes in the microwave conductivity of the medium with nanosecond time resolution. 相似文献
74.
Hoogboom J Clerx J Otten MB Rowan AE Rasing T Nolte RJ 《Chemical communications (Cambridge, England)》2003,(23):2856-2857
The directional drying of a low-salt Tris-EDTA (TE)-buffer to give an alignment layer offers a simple, one-step, non-contact procedure for the construction of parallel liquid crystal displays (LCDs), which can be used to amplify the presence of DNA to scales visible to the naked eye, opening up possibilities for easy detection of bio recognition events. 相似文献
75.
Chaos Theory and the Problem of Change in Family Systems 总被引:1,自引:0,他引:1
In spite of the fact that nonlinear dynamical models have been used for almost half a century in the area of family process theory, an appreciation of the potential of chaos models is a relatively recent development. The present paper discusses the shift of focus in our understanding of family processes resulting from Prigogine's chaos framework, and outlines a chaos approach to family interaction. It is argued that this approach allows us to more effectively address one of the central outstanding questions in the field, namely, how self regulatory behavior can contribute to structural transformation of the family system. 相似文献
76.
Diggle SP Matthijs S Wright VJ Fletcher MP Chhabra SR Lamont IL Kong X Hider RC Cornelis P Cámara M Williams P 《Chemistry & biology》2007,14(1):87-96
Pseudomonas aeruginosa produces 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), a quorum-sensing (QS) signal that regulates numerous virulence genes including those involved in iron scavenging. Biophysical analysis revealed that 2-alkyl-3-hydroxy-4-quinolones form complexes with iron(III) at physiological pH. The overall stability constant of 2-methyl-3-hydroxy-4-quinolone iron(III) complex was log beta(3) = 36.2 with a pFe(3+) value of 16.6 at pH 7.4. PQS was found to operate via at least three distinct signaling pathways, and its precursor, 2-heptyl-4-quinolone (HHQ), which does not form an iron complex, was discovered to function as an autoinducer molecule per se. When PQS was supplied to a P. aeruginosa mutant unable to make pyoverdine or pyochelin, PQS associated with the cell envelope and inhibited bacterial growth, a finding that reveals a secondary function for PQS in iron entrapment to facilitate siderophore-mediated iron delivery. 相似文献
77.
Capillary electrophoresis (CE), using highly-sulfated cyclodextrins as chiral selectors, has been applied to determine the chiral purity of pharmaceutical compounds. A chiral separation strategy, developed earlier for racaemic mixtures, was applied on four basic drugs (propranolol, atenolol, chlorpheniramine and tryptophan methylester). The aim was to develop validated separation methods which allow determination of 0.1% impurity levels of the unwanted enantiomers (distomer) in the presence of 99.9% of the active compound (eutomer). The linearity, quantification limits for the trace enantiomers and the precision of the measurements were determined. In a second part, impurity separations have been simulated in order to evaluate the required resolution when assaying impurities. It is shown that a baseline resolution of 1.5, generally accepted for racaemic mixtures, does not always allow good impurity determinations. Two alternative methods to solve this problem have been proposed. 相似文献
78.
Dr. Ludovic Bretin Yurii Husiev Dr. Vadde Ramu Liyan Zhang Matthijs Hakkennes Selda Abyar Andrew C. Johns Dr. Sylvia E. Le Dévédec Dr. Tania Betancourt Dr. Alexander Kornienko Dr. Sylvestre Bonnet 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(5):e202316425
Photoactivated chemotherapy (PACT) is a promising cancer treatment modality that kills cancer cells via photochemical uncaging of a cytotoxic drug. Most ruthenium-based photocages used for PACT are activated with blue or green light, which penetrates sub-optimally into tumor tissues. Here, we report amide functionalization as a tool to fine-tune the toxicity and excited states of a terpyridine-based ruthenium photocage. Due to conjugation of the amide group with the terpyridine π system in the excited state, the absorption of red light (630 nm) increased 8-fold, and the photosubstitution rate rose 5-fold. In vitro, red light activation triggered inhibition of tubulin polymerization, which led to apoptotic cell death both in normoxic (21 % O2) and hypoxic (1 % O2) cancer cells. In vivo, red light irradiation of tumor-bearing mice demonstrated significant tumor volume reduction (45 %) with improved biosafety, thereby demonstrating the clinical potential of this compound. 相似文献
79.
Matthijs van der Knaap José M. Otero Antonio Llamas-Saiz Mark J. van Raaij Lianne I. Lageveen Henk J. Busscher Gijsbert M. Grotenbreg Gijsbert A. van der Marel Herman S. Overkleeft Mark Overhand 《Tetrahedron》2012,68(10):2391-2400
The strategic replacement of four α-amino acid residues of a cyclo-(ααααα)2 peptide by β-, β2- or β3-amino acids residues provided a series of novel 2:1 α/β-mixed peptides that were designed to adopt cyclic hairpin-like structures. It was shown that conformationally stable cyclo-(αβαβα)2 isomers can be obtained using both enantiomers of the central two basic α-amino acid residues, a known α-amino acid turn sequence and several combinations of facing β-amino acid residues with no side chain or a hydrophobic side chain having specific regio- and stereochemistry. The X-ray analysis of two derivatives provides molecular details of the intra-molecular hydrogen bonding interaction, dihedral angles of the backbone and side chain positioning of the novel cyclic hairpin-like structures. One of these isomers forms an unprecedented hexagon-shaped nano-channel assembly in the crystal structure. Well-defined cyclic hairpin-like structures as described here and derivatives that can be readily designed based on this research can be used as scaffolds onto which functional groups can be grafted in a spatially controlled manner and as β-hairpin mimics with specific biological properties. 相似文献
80.
Thommes M Smarsly B Groenewolt M Ravikovitch PI Neimark AV 《Langmuir : the ACS journal of surfaces and colloids》2006,22(2):756-764
We report results of nitrogen and argon adsorption experiments performed at 77.4 and 87.3 K on novel micro/mesoporous silica materials with morphologically different networks of mesopores embedded into microporous matrixes: SE3030 silica with worm-like cylindrical channels of mode diameter of approximately 95 angstroms, KLE silica with cage-like spheroidal pores of ca. 140 angstroms, KLE/IL silica with spheroidal pores of approximately 140 angstroms connected by cylindrical channels of approximately 26 angstroms, and, also for a comparison, on Vycor glass with a disordered network of pores of mode diameter of approximately 70 angstroms. We show that the type of hysteresis loop formed by adsorption/desorption isotherms is determined by different mechanisms of condensation and evaporation and depends upon the shape and size of pores. We demonstrate that adsorption experiments performed with different adsorptives allow for detecting and separating the effects of pore blocking/percolation and cavitation in the course of evaporation. The results confirm that cavitation-controlled evaporation occurs in ink-bottle pores with the neck size smaller than a certain critical value. In this case, the pressure of evaporation does not depend upon the neck size. In pores with larger necks, percolation-controlled evaporation occurs, as observed for nitrogen (at 77.4 K) and argon (at 87.3 K) on porous Vycor glass. We elaborate a novel hybrid nonlocal density functional theory (NLDFT) method for calculations of pore size distributions from adsorption isotherms in the entire range of micro- and mesopores. The NLDFT method, applied to the adsorption branch of the isotherm, takes into account the effect of delayed capillary condensation in pores of different geometries. The pore size data obtained by the NLDFT method for SE3030, KLE, and KLE/IL silicas agree with the data of SANS/SAXS techniques. 相似文献