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Recognition Studies (recognition + studies)
Selected AbstractsSynthesis, Protonation and CuII Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition StudiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009Andrés G. Algarra Abstract The synthesis and coordination chemistry of two novel ligands, 2,6,9,12,16-pentaaza[17]metacyclophane (L1) and 2,6,9,12,16-pentaaza[17]paracyclophane (L2), is described. Potentiometric studies indicate that L1 and L2 form a variety of mononuclear complexes the stability constants of which reveal a change in the denticity of the ligand when moving from L1 to L2, a behaviour that can be qualitatively explained by the inability of the paracyclophanes to simultaneously use both benzylic nitrogen atoms for coordination to a single metal centre. In contrast, the formation of dinuclear hydroxylated complexes is more favoured for the paraL2 ligand. DFT calculations have been carried out to compare the geometries and relative energies of isomeric forms of the [CuL]2+ complexes of L1 and L2 in which the cyclophane acts either as tri- or tetradentate. The results indicate that the energy cost associated with a change in the coordination mode of the cyclophane from tri- to tetradentate is moderate for both ligands so that the actual coordination mode can be determined not only by the characteristics of the first coordination sphere but also by the specific interactions with additional nearby water molecules. The kinetics of the acid promoted decomposition of the mono- and dinuclear CuII complexes of both cyclophanes have also been studied. For both ligands, dinuclear complexes convert rapidly to mononuclear species upon addition of excess acid, the release of the first metal ion occurring within the mixing time of the stopped-flow instrument. Decomposition of the mononuclear [CuL2]2+ and [CuHL2]3+ species occurs with the same kinetics, thus showing that protonation of [CuL2]2+ occurs at an uncoordinated amine group. In contrast, the [CuL1]2+ and [CuHL1]3+ species show different decomposition kinetics indicating the existence of significant structural reorganisation upon protonation of the [CuL1]2+ species. The interaction of AMP with the protonated forms of the cyclophanes and the formation of mixed complexes in the systems Cu,L1 -AMP, Cu,L2 -AMP, and Cu,L3 -AMP, where L3 is the related pyridinophane containing the same polyamine chain and 2,6-dimethylpyridine as a spacer, is also reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Anthracene-Coupled Pyridine Amines: A New "Off-On" Switch for Molecular Recognition Studies on Dicarboxylic Acids.CHEMINFORM, Issue 35 2006Kumaresh Ghosh Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Enhancing therapeutic loading and delaying transport via molecular imprinting and living/controlled polymerizationAICHE JOURNAL, Issue 1 2010Asa D. Vaughan Abstract This work demonstrates for the first time molecular imprinting using a "living/controlled" polymerization (LCP) strategy to enhance template loading/affinity and delay release in weakly crosslinked gels. Two gel systems were studied: poly(DEAEM- co -HEMA- co -PEG200DMA) gels imprinted for diclofenac sodium and poly(MAA- co -EGDMA) gels imprinted for ethyl adenine-9-acetate. Experimental evidence confirms that template diffusion coefficients within imprinted gels can be heavily influenced by template binding affinity. Recognition studies revealed significant increases in template loading/affinity with large increases in loading for LCP, and dynamic template release studies showed that imprinting via LCP extends the template release profile by twofold over that of imprinting via conventional free-radical polymerization techniques and fourfold over the control network (less Fickian and toward zero-order release with a profile coefficient of 0.70). Analysis of reaction kinetics indicated that LCP with reversible termination events increases the chemically controlled chain propagation mechanism, and that binding sites are formed during this phase of the polymerization. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Are surface properties integrated into visuohaptic object representations?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2010Simon Lacey Abstract Object recognition studies have almost exclusively involved vision, focusing on shape rather than surface properties such as color. Visual object representations are thought to integrate shape and color information because changing the color of studied objects impairs their subsequent recognition. However, little is known about integration of surface properties into visuohaptic multisensory representations. Here, participants studied objects with distinct patterns of surface properties (color in Experiment 1, texture in Experiments 2 and 3) and had to discriminate between object shapes when color or texture schemes were altered in within-modal (visual and haptic) and cross-modal (visual study followed by haptic test and vice versa) conditions. In Experiment 1, color changes impaired within-modal visual recognition but had no effect on cross-modal recognition, suggesting that the multisensory representation was not influenced by modality-specific surface properties. In Experiment 2, texture changes impaired recognition in all conditions, suggesting that both unisensory and multisensory representations integrated modality-independent surface properties. However, the cross-modal impairment might have reflected either the texture change or a failure to form the multisensory representation. Experiment 3 attempted to distinguish between these possibilities by combining changes in texture with changes in orientation, taking advantage of the known view-independence of the multisensory representation, but the results were not conclusive owing to the overwhelming effect of texture change. The simplest account is that the multisensory representation integrates shape and modality-independent surface properties. However, more work is required to investigate this and the conditions under which multisensory integration of structural and surface properties occurs. [source] Classic and false memory designs: An electrophysiological comparisonPSYCHOPHYSIOLOGY, Issue 5 2004Doreen Nessler Abstract In false memory tasks new items either overlap with the semantic concepts of studied items (LURE) or do not (NEW). ERP differences between OLD and NEW items in false memory tasks have been interpreted as similar to episodic memory effects observed in classic recognition studies. However, NEW items in a false memory task can be rejected on the basis of semantic information alone, a strategy useless in classic tasks. Here a medial frontal (400 to 500 ms) episodic memory effect was revealed in both classic and false memory tasks, whereas a parietal (500 to 700 ms) episodic memory effect was found only in the classic task. In the false memory task a large, parietally focused positivity was evident for NEW items, assumed to reflect a targetlike response to new semantic information. The brain activity underlying false memory effects, therefore, cannot be interpreted as a straightforward example of that arising during a standard recognition task. [source] Memory of children's faces by adults: Appearance does matter,APPLIED COGNITIVE PSYCHOLOGY, Issue 7 2009Vicki Silvers Gier Accurately detecting faces of children when their appearance has been altered is especially important in recognizing abducted or missing child. Face recognition studies have focussed on recognizing the adult perpetrator; however, there is lack of research on recognizing a child's face under different appearances. Two studies were conducted to determine what type of photos may increase recognition of missing children. In Experiment 1 participants were shown pictures of children's faces in a study phase in which their faces were either dirtied with negative affect or clean with positive affect, followed by a recognition phase. Accuracy and confidence were higher when the face at recognition was the same type as in the study phase. Experiment 2 replicated Experiment 1, adding four delay conditions: 10-minute interval (10-MI), 3, 6 or 12 week. Accuracy and confidence decreased over time and we again found a significant interaction between face at study and face at recognition. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||