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Memory Effects (memory + effects)
Selected AbstractsMemory Effects in Palladium-Catalyzed Allylic Alkylations of 2-Cyclohexen-1-yl AcetateADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17-18 2007Nina Svensen Abstract The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employed were (,3 -allyl)PdLCl, where L is a monophosphine ligand [PPh3, PCy3, P(2-BiPh)Cy2, or P(t- Bu)3], all of which afforded enantiospecificity to some extent (5,47,%). Quantum mechanical calculations show that, theoretically, the enantiospecificity should be high due to a preference for the "trans to P" transition state in both formation of the ,3 -allyl intermediate and nucleophilic attack. However, the observed enantiospecificity is relatively low due to isomerization of the ,3 -allyl intermediate and/or dynamic equilibria between the catalytically active (,3 -allyl)PdLCl species and [(,3 -allyl)PdL2]+ or [(,3 -allyl)PdCl]2. It was also observed experimentally that increasing the bulk of the phosphine inhibits formation of the [(,3 -allyl)PdL2]+ complexes, significantly increasing the observed enantiospecificity for some of the ligands. [source] Rapid capillary electrophoresis time-of-flight mass spectrometry separations of peptides and proteins using a monoquaternarized piperazine compound (M7C4I) for capillary coatingsELECTROPHORESIS, Issue 8 2008Anisa Elhamili Abstract A monoquaternarized piperazine, 1-(4-iodobutyl) 4-aza-1-azoniabicyclo[2,2,2] octane iodide (M7C4I), has been evaluated as a surface derivatization reagent for CE in combination with TOF MS for the analysis of proteins, peptides, and protein digests. The M7C4I piperazine, at alkaline pH, forms a covalent bond via alkylation of the ionized silanols producing a cationic surface with a highly stable and reversed EOF. The obtained surface yields rapid separations (less than 5,min) of peptides and proteins at acidic pH with high separation efficiencies (up to 1.1×106 plates/m for peptides and up to 1.8×106 plates/m for proteins) and no observed bleeding of the coating reagent into the mass spectrometer. The simplicity of the coating procedure also enables fast (2,min) regeneration of the surface, if necessary. This is useful in the analysis of complex samples in order to prevent possible memory effects. The potential of using M7C4I-coated capillaries for MS analysis of complex samples is demonstrated by the separation of peptides, proteins, and protein digests. Even more, the spectacular thing in which large intact proteins with molecular masses over 0.5,MDa could be separated. The coating showed good ability to handle these large proteins with high efficiency and retained peak shape as demonstrated by separation of IgG1 (150,kDa) and thyroglobulin (669,kDa). [source] Illusory and spurious correlations: distinct phenomena or joint outcomes of exemplar-based category learning?EUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 3 2006Thorsten Meiser Stereotype formation about novel groups was analyzed with trivariate stimulus distributions that were generated by group membership, valence of behavior, and a context variable. Within this stimulus setting, we manipulated the confounding role of the context variable and the distinctiveness of events in terms of their relative infrequency. The experimental procedure allowed us to analyze illusory and spurious correlations in a joint framework, to conduct focused tests for memory effects of relative infrequency and to investigate the detection of covariations with the context variable. The results revealed that illusory and spurious correlations were formed without enhanced memory for infrequent events and with existing covariations of the confounding context factor being well extracted. These observations suggest that illusory and spurious correlations can be understood without assuming specific cognitive processes that are tied to the particular characteristics of a given stimulus distribution, such as enhanced memory in the case of relative infrequency and neglect of a context variable in the case of a confounding factor. Instead, computer simulations with an exemplar-based learning model demonstrated that exemplar-based category learning may provide a coherent and integrative theoretical framework for illusory correlations, spurious correlations and true contingency learning in social cognition. Copyright © 2006 John Wiley & Sons, Ltd. [source] Polymer/NiTi-composites: Fundamental Aspects, Processing and Properties,ADVANCED ENGINEERING MATERIALS, Issue 11 2005K. Neuking NiTi shape memory alloys can be used as actor materials and perform mechanical work; they can also be used for damping applications. In combination with polymers their functionality can be increased. Shape memory effects of NiTi alloys are associated with large strains and in a NiTi/polymer-composite, the polymer can accommodate these large strains without breaking. In a NiTi/polymer-composite the polymer can for example be used to store elastic energy, to provide corrosion resistance or to assist in a damping application. For all applications, a good bonding between the shape memory alloy and the polymer is required. The present paper considers fields of applications, processing and properties of NiTi/polymer-composites. [source] Incremental model for fatigue crack growth based on a displacement partitioning hypothesis of mode I elastic,plastic displacement fieldsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 7 2007S. POMMIER ABSTRACT The mode I displacement field in the near crack tip region is assumed to be depicted by its partition into an elastic field and a plastic field. Then, each part of the displacement field is also assumed to be the product of a reference field, a function of space coordinates only, and of an intensity factor, function of the loading conditions. This assumption, classical in fracture mechanics, enables one to work at the global scale since fracture criteria can be formulated as a function of the stress intensity factors only. In the present case, the intensity factor of the plastic part of the displacement field measures crack tip plastic flow rate at the global scale. On the basis of these hypotheses, the energy balance equation and the second law of thermodynamics are written at the global scale, i.e. the scale of the K-dominance area. This enables one to establish a yield criterion and a plastic flow rule for the crack tip region. Then, assuming a relation between plastic flow in the crack tip region and fatigue crack growth allows an incremental model for fatigue crack growth to be built. A few examples are given to show the versatility of the model and its ability to reproduce memory effects associated with crack tip plasticity. [source] A parameter-reduced volterra model for dynamic RF power amplifier modeling based on orthonormal basis functionsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2007M. Isaksson Abstract A nonlinear dynamic behavioral model for radio frequency power amplifiers is presented. It uses orthonormal basis functions, Kautz functions, with complex poles that are different for each nonlinear order. It has the same general properties as Volterra models, but the number of parameters is significantly smaller. Using frequency weighting the out-of-band model error can be reduced. Using experimental data it was found that the optimal poles were the same for different input powers and for the different nonlinear orders. The optimal poles were also the same for direct and inverse models, which could be explained theoretically to be a general property of nonlinear systems with negligible linear memory effects. The model can be used as either a direct or inverse model with the same model error for power amplifiers with negligible linear memory effects. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] Verbal and Nonverbal Memory in Adults Prenatally Exposed to AlcoholALCOHOLISM, Issue 5 2010Claire D. Coles Background:, Neurocognitive effects of prenatal alcohol exposure in adulthood are not well documented. Questions persist regarding the extent to which there are specific, measurable effects beyond those associated with global ability deficits, whether individuals without the full fetal alcohol syndrome (FAS) demonstrate alcohol-related cognitive impairments, and whether observed memory effects are specific to a particular modality, i.e., verbal vs. visual/spatial domains. Methods:, In this study, verbal and nonverbal selective reminding paradigms were used to assess memory function in 234 young adults (M age: 22.78, SD: 1.79). Alcohol exposure was quantified prenatally. Alcohol groups included: Individuals with physical effects of alcohol exposure (Dysmorphic group, n = 47); Exposed individuals without such effects (n = 74). Contrast groups included: Controls (n = 59) matched for ethnicity, socioeconomic status, and hospital of birth; Special Education contrast group (n = 54) included to control for disability status. Memory outcomes entailed total recall, delayed recall, and measures of encoding and retrieval, and learning over trials as indexed by slope. Results:, Results indicated that Dysmorphic individuals were significantly less efficient in memory performance than Controls on all of the outcomes measured, but they did not differ from those in the Special Education contrast group. The nondysmorphic, alcohol-exposed group was intermediate in their performance, suggesting a continuum of effects of prenatal exposure. Evaluation of the encoding and retrieval aspects of memory performance indicated that learning rather than forgetting accounted for the deficits associated with prenatal alcohol exposure. Finally, no interaction was found between modality of presentation (verbal and nonverbal) and effects of alcohol exposure on memory performance. Conclusion:, These findings indicate that prenatal alcohol exposure is associated with persistent and specific effects on memory performance, and these problems result from less efficient encoding of information across both verbal and nonverbal modalities. Education and training efforts with this clinical group should take these characteristics into account. [source] Stability of global and exponential attractors for a three-dimensional conserved phase-field system with memoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2009Gianluca Mola Abstract We consider a conserved phase-field system on a tri-dimensional bounded domain. The heat conduction is characterized by memory effects depending on the past history of the (relative) temperature ,, which is represented through a convolution integral whose relaxation kernel k is a summable and decreasing function. Therefore, the system consists of a linear integrodifferential equation for ,, which is coupled with a viscous Cahn,Hilliard type equation governing the order parameter ,. The latter equation contains a nonmonotone nonlinearity , and the viscosity effects are taken into account by a term ,,,,t,, for some ,,0. Rescaling the kernel k with a relaxation time ,>0, we formulate a Cauchy,Neumann problem depending on , and ,. Assuming a suitable decay of k, we prove the existence of a family of exponential attractors {,,,,} for our problem, whose basin of attraction can be extended to the whole phase,space in the viscous case (i.e. when ,>0). Moreover, we prove that the symmetric Hausdorff distance of ,,,, from a proper lifting of ,,,0 tends to 0 in an explicitly controlled way, for any fixed ,,0. In addition, the upper semicontinuity of the family of global attractors {,,,,,} as ,,0 is achieved for any fixed ,>0. Copyright © 2009 John Wiley & Sons, Ltd. [source] Positivity and time behavior of a linear reaction,diffusion system, non-local in space and timeMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2008Andrii Khrabustovskyi Abstract We consider a general linear reaction,diffusion system in three dimensions and time, containing diffusion (local interaction), jumps (nonlocal interaction) and memory effects. We prove a maximum principle and positivity of the solution and investigate its asymptotic behavior. Moreover, we give an explicit expression of the limit of the solution for large times. In order to obtain these results, we use the following method: We construct a Riemannian manifold with complicated microstructure depending on a small parameter. We study the asymptotic behavior of the solution to a simple diffusion equation on this manifold as the small parameter tends to zero. It turns out that the homogenized system coincides with the original reaction,diffusion system. Using this and the facts that the diffusion equation on manifolds satisfies the maximum principle and its solution converges to a easily calculated constant, we can obtain analogous properties for the original system. Copyright © 2008 John Wiley & Sons, Ltd. [source] A highly efficient class-F power amplifier for wideband linear power amplifier applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009Jangheon Kim Abstract In this letter, a highly efficient class-F power amplifier (PA) is developed as a new main block of the wideband base-station linear power amplifier. The class-F PA is implemented using Eudyna EGN010MK GaN HEMT with a 10-W peak envelop power. The nonlinearity and memory effects of class-F PA are explored to apply the wideband application. The maximum power-added efficiency of the implemented PA is 68% at a saturated output power of 40 dBm for the 2.14-GHz CW signal. The PA delivers a good efficiency of 35% at an average output power of 32.3 dBm for wide-band code division multiple access 3FA signal with 15-MHz bandwidth, and the linearity can be improved to about ,48 dBc using the digital feedback predistortion linearization technique. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2323,2326, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24631 [source] Synergistic digital predistorter based on a low memory power amplifier for wideband linearizationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009Jangheon Kim Abstract We investigate on linearization performance of a digital predistortion (DPD) linearization technique based on the low memory power amplifier (PA) for wideband signals. The low memory PA is implemented using a 90W PEP LDMOSFET at 2.14 GHz, and an envelope short matching topology is applied at the active ports to minimize memory effects. To explore memory effects of the implemented amplifier, the amplifier is tested through two-tone signals (up to 20 MHz tone spacing). The proposed DPD technique is compared with DPD technique based on a PA exhibiting serious memory effects for a forward-link WCDMA 3FA signal with 15-MHz bandwidth. The experimental result shows that the proposed DPD scheme has better linearization performance than the conventional digital predistorter and lower computational complexity over the conventional wideband digital predistorters. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1548,1552, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24357 [source] Electro-thermal theory of the switching and memory effects in chalcogenide glassy semiconductorsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2009Konstantin Tsendin Abstract A brief review of the most important results of electro-thermal theory of switching and memory effects is presented. It is shown that this theory is able to explain the large scope of the switching and memory effect experimental findings, including the endurance of modern memory cells. [source] Fabrication of carbon nanotube-based field-effect transistors for studies of their memory effectsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007M. Y. Zavodchikova Abstract Carbon nanotube-based field-effect transistors (CNTFETs) have been fabricated using nanometer thin dielectric material as the gate insulator film. The demonstrated fabrication technique is highly suitable for preparing devices with low contact resistances between the electrodes and the carbon nanotube, down to 14 k,. Electronic transport measurements of the fabricated devices have been conducted on more than 70 FETs. Hysteretic behavior in the transfer characteristics of some CNTFETs was observed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Process simulation of p -doping in GaN and related group III nitridesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007Y. J. Zhou Abstract In this work we use the PROCOM sofware to model Mg doped GaN film growth by MOCVD. The 2/3D conservation equations of mass, energy, momentum and species are solved by the nonsymmetric conjugate gradient method with block preconditioning (H. C. Elman, Preconditioned conjugate gradient methods for nonsymmetric systems of linear equations (Yale University Research Report, 1981) [5]). A kinetics model with gas/surface adduct formation has been incorporated with detailed Mg dopant reaction mechanism. We reproduced broad doping profiles caused by memory effects and verified that the formation of (NH3)2 -MgCp2 and NH3 -MgCp2 adducts play an important role in p-doping of GaN and related Group III nitrides. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Single photon correlation measurements in a study of excitation process of individual CdTe/ZnTe quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006J. Suffczy Abstract We present the results of systematic autocorrelation and cross-correlation measurements performed on photons originating from various excitonic transitions in a single CdTe/ZnTe quantum dot (QD). Excitation power dependence of photoluminescence intensity was also measured on the same dot under the same experimental conditions. Recorded correlation histograms have provided evidence for memory effects in QD photoluminescence extending over a few excitation periods. Rate equation model assuming a ladder of states and excitation through a single carrier and exciton capture, is fitted to the data. As a consequence, simultaneous quantitative description of the results of both, correlation and power dependence, is obtained. Strong evidence is presented for a QD excitation by capture of single carriers rather than entire excitons. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical transport in strained La0.7Ca0.3MnO3 filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2006V. Markovich Abstract Magnetotransport properties of La0.7Ca0.3MnO3 thin films deposited on (100) LaAlO3 substrate were investigated. Fine balance between the charge ordered insulating phase and ferromagnetic metallic phase results in a number of glassy features such as: significant hysteresis, memory effects and long-time resistivity relaxation at turning on and off of magnetic field. It was found that in the temperature range 10,220 K the resistance of thin film decreases significantly upon applying electric current and this effect cannot be explained by homogeneous Joule heating. The magnetotransport properties of the thin films are discussed in the frame of cross-coupling of charge, spin and strain. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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] Source memory for the color of pictures: Event-related brain potentials (ERPs) reveal sensory-specific retrieval-related activityPSYCHOPHYSIOLOGY, Issue 3 2003Yael M. Cycowicz Abstract Remembering the context (i.e., source) in which an event occurred reveals episodic memory effects (EM) in the event-related brain potentials (ERP). In some verbal source memory experiments, a late prefrontal EM effect has been observed. In a different, pictorial source memory paradigm, a late, parieto-occipital EM effect was recorded. To assess whether these two EM effects stemmed from differences in task paradigms or from source-attribute differences, ERPs were recorded during source memory retrieval for object colors in two tasks. In the sequential task, old/new judgments were followed by source judgments (i.e., color). In the exclusion task, source memory judgments coincided with recognition judgments. For both tasks, late, parietao-occipital EM effects were observed. These findings suggest that it is not the nature of the task, but rather the perceptual characteristics of the source that lead to the presence of the parieto-occipital EM effect. The data further imply that memories for perceptual attributes such as color are stored in and retrieved from sensory-specific cortical areas. [source] Hydrogen and oxygen isotopes of water from inclusions in minerals: design of a new crushing system and on-line continuous-flow isotope ratio mass spectrometric analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009Yuri V. Dublyansky An analytical line for stable isotope analyses of water recovered from fluid inclusions in minerals was built and successfully tested. The line is based on the principle of continuous-flow analysis of water via high-temperature reduction on glassy carbon. It includes a custom-designed set of high-efficiency crushers and a cryo-focusing cell. This paper provides details of the line design and discusses strategies for line conditioning and mitigation of memory effects. The line allows measurements of hydrogen and oxygen isotopes during a single acquisition. The precision of the analyses depends on the amount of water released from the inclusions. The best results are obtained for samples containing at least 0.1,0.2,µL (0.06,0.11,µmol) H2O. For such samples precision is better than 1.5, for ,D and 0.5, for ,18O (1,). Smaller amounts of water can be measured but at lower precision. Analyses of modern calcite formed under stable conditions in a deep cave allowed assessment of the accuracy of the analyses. The ,D values measured in fluid inclusions of this working standard match the ,D value of the parent water, and the oxygen isotope values agree within ca. 0.5,. This indicates that fluid inclusions trapped in calcite at near-ambient temperatures (e.g. speleothems and low-temperatures phreatic calcite) faithfully preserve the original isotopic composition of the parent waters. Copyright © 2009 John Wiley & Sons, Ltd. [source] A new continuous flow isotope ratio mass spectrometry system for the analysis of ,2H, ,17O and ,18O of small (120,,g) water samples in atmospheric applicationsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004Peter Franz A new continuous-flow system for the analysis of the complete stable isotopic composition of water vapor has been developed. The sample size is reduced to only 120,,g (,120,nL of liquid substance) of water, yielding precisions of about 0.7, 1.3 and 7, for ,17O, ,18O and ,2H, respectively. The total time for the analysis of a sample is about 150 min including purging times. Oxidized steel surfaces can be a source of memory effects which can be corrected for. The system is predestined for atmospheric applications in the tropopause region, as the sample can be directly introduced into the system from a cryogenic trap. Copyright © 2004 John Wiley & Sons, Ltd. [source] When goals constrain: Eye movements and memory for goal-Oriented map studyAPPLIED COGNITIVE PSYCHOLOGY, Issue 6 2009Tad T. Brunyé Perspective goals, such as studying a map to learn a route through an environment or the overall layout of an environment, produce memory congruent with the goal-directed rather than the studied perspective. One explanation for this finding is that perspective goals guide attention towards actively gathering relevant information during learning. A second explanation is that information is automatically organized into a goal-congruent spatial model that guides retrieval. Both explanations predict goal-congruent memory, but only the former one predicts eye movement differences during study. The present experiment investigated the effect of perspective goals on eye movement during map study and the flexibility of resulting spatial memories. Results demonstrate eye movements towards goal-congruent map elements during learning, and lasting memory effects at test. These findings carry implications for the design of adaptive hand-held and in-vehicle navigation interfaces that accommodate for varied user goals. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||