Self-terminating Process Research Articles

Fabrication of gold tips suitable for tip-enhanced Raman spectroscopy

The authors report on a simple method of fabricating gold tips, suitable for use in a shear-force mode atomic force microscope for tip-enhanced Raman spectroscopy (TERS). The proposed electrochemical method is highly optimized and offers five advantages: produces a low-aspect ratio tip that can withstand the lateral force at the end of the tip during scanning, produces a sharp tip end to generate good Raman enhancements for TERS, a self-terminating process that makes the etching process easy, use of inexpensive electronic systems so that it can be adopted by any laboratory, and less time consuming (takes less than 20s to fabricate a single tip). This article demonstrates TERS imaging using such tips.

Mechanism investigation of Prussian blue electrochemically deposited from a solution containing single component of ferricyanide

Prussian white (a reduced state of Prussian blue) was electrochemically deposited on a polycrystalline Pt electrode from an acidic solution of ferricyanide. Electrochemical measurements showed that the formation of Prussian white on platinum electrode was a self-terminated process. A compacted PB film can be formed by using both potential scanning and potentiostatic methods as confirmed by AFM measurement. In situ FTIR measurements were carried out to explore the formation mechanism. The new band arising at 2075 cm −1 is assigned to the characteristic absorbance of CN of Prussian white, while the band at 2104 cm −1 is due to the absorbance of CN of Prussian blue. A possible mechanism of electrodeposition of Prussian white was discussed.

A strong test of the dual-mode hypothesis

One account of facial cognition, the dual-mode hypothesis, maintains that there are two sources of information in a human face, featural and configural, and that these sources are processed simultaneously and independently of one another. According to the hypothesis, the processing and identification of upright faces relies primarily on configural information, and this information is disrupted to such an extent upon inversion as to result in a reliance on featural information for identifying inverted faces (e.g., Searcy & Bartlett, 1996). When considered in terms of the general characteristics of human information processing, the foundational assumptions of the dual-mode hypothesis are as follows: Facial information processing is accomplished by a parallel self-terminating architecture with unlimited capacity to supercapacity and a preservation of independence between the rates of processing of featural and configural information. Although a number of studies have provided evidence consistent with the dual-mode hypothesis, until now there have been no direct tests of the foundational assumptions of the hypothesis. The present study provides that direct test, providing strong support for three of the assumptions (parallel self-terminating processing with unlimited capacity to supercapacity) while contradicting a fourth (independence in rates).

Developmental influences on auditory perception in female zebra finches - is there a sensitive phase for song preference learning?

AbstractSong plays an important role in mate choice in oscine songbirds. Male advertising song is culturally transmitted resulting in individual- or population-specific song variants. Evidence is accumulating that female song preferences are influenced by those song variants they experienced when young, but the nature and timing of the acquisition process itself is still poorly understood. Song acquisition (as well as sexual imprinting) has been studied in more detail in zebra finches (Taeniopygia guttata) than in any other songbird species, making it timely to review the consequences of early exposure on female song perception in this species. The current literature provides substantial evidence not only for preference learning but also for exposure-dependent perceptual fine-tuning. Sensitivity for song preference learning changes over the course of development. Preference learning does not seem to occur earlier than 25 days of age (hence paralleling the time course for song acquisition in males), but a potential endpoint is currently less obvious. However, studies so far have focussed on the outcome rather than the process of learning, and thus have not aimed at delineating a sensitive phase. Early acquired song preferences seem highly stable regardless of additional experience, which suggests a self-terminating process as previously found for sexual imprinting. There are still obvious gaps in our understanding of the mechanisms underlying the process of song preference learning, but these seem worthwhile addressing, as the consequences for mate choice might differ dramatically depending on when and from whom learning takes place.

On the Production of Superheavy Elements

▪ Abstract In the first century of nuclear physics, 31 radioactive elements were added to the periodic system of elements. In 1996, at GSI, element 112 was synthesized by fusion of70Zn with208Pb, and its atomic number was established by a decay chain linked to known isotopes. Relativistic mean field calculations of the ground-state stability of nuclei predict the next spherical proton shell not as previously assumed at Z = 114 but at Z = 120 for304184120. Moreover, a region of spherical nuclei with depleted central density is predicted at N = 172 for292172120 by mean field calculations. New elements are established today using recoil separators combined with decay-chain analysis. Three new elements, Z = 110–112, and 18 transactinide isotopes have been discovered since 1985, all assigned by genetical linkage to known isotopes. The production cross sections decrease exponentially going to higher elements and now have reached the 1-pb limit. Fusion aiming at higher and higher atomic numbers is a self-terminated process because of constantly increasing disruptive Coulomb forces. The limitations in the formation and deexcitation stages are presented. The rapid drop to smaller cross sections (“Coulomb falls”) is modified by nuclear structure not only in the ground state of the final product (superheavy element) but also in the collision partners and during the amalgamation process (closed shells and clusters). The prospects to produce higher elements and new isotopes by extrapolating the physics learned from reaching Z = 112 are283114, which might be found in76Ge/208Pb at a level of 0.1 pb and linked to259No. At this level, about 30 transactinide isotopes are still in reach. To explain the stabilization of production cross sections in the pb range claimed in 1999 experiments, new physics delaying the descent in the “Coulomb falls” is to appear. For the FLNR experiments claiming Z = 114, no explanation is offered. For the LBL experiment claiming Z = 118, an explanation from new physics is presented. All experiments need confirmation. Verifying the centrally depleted, spherical nuclei around292172120 would be a victory for nuclear structure physics, much more interesting than the trivial case of another doubly closed shell nucleus.

Visual Search for Change: A Probe into the Nature of Attentional Processing

A set of visual search experiments tested the proposal that focused attention is needed to detect change. Displays were arrays of rectangles, with the target being the item that continually changed its orientation or contrast polarity. Five aspects of performance were examined: linearity of response, processing time, capacity, selectivity, and memory trace. Detection of change was found to be a self-terminating process requiring a time that increased linearly with the number of items in the display. Capacity for orientation was found to be about five items, a value comparable to estimates of attentional capacity. Observers were able to filter out both static and dynamic variations in irrelevant properties. Analysis also indicated a memory for previously attended locations. These results support the hypothesis that the process needed to detect change is much the same as the attentional process needed to detect complex static patterns. Interestingly, the features of orientation and polarity were found to be handled in somewhat different ways. Taken together, these results not only provide evidence that focused attention is needed to see change, but also show that change detection itself can provide new insights into the nature of attentional processing.

Parallel Processing Response Times and Experimental Determination of the Stopping Rule

It was formerly demonstrated that virtually all reasonable exhaustive serial models, and a more constrained set of exhaustive parallel models, cannot predict critical effects associated with self-terminating models. The present investigation greatly generalizes the parallel class of models covered by similar “impossibility” theorems. Specifically, we prove that if an exhaustive parallel model is not super capacity, and if targets are processed at least as fast as non-targets, then it cannot predict such (self-terminating) effects. Such effects are ubiquitous in the experimental literature, offering strong confirmation for self-terminating processing.

Spatio-temporal Properties of Elementary Perception: An Investigation of Parallel, Serial, and Coactive Theories

A mathematical theory and related experimental methodology are developed that permit strong, converging tests of parallel versus serial versus channel summation processing and of exhaustive versus self-terminating processing. An experimental design is used for two studies, in which the presence or absence of a target in each of two positions, is factorially combined with two levels of brightness (a version of the double factorial paradigm). When both targets are present (redundant target condition) the two levels of brightness permit factorial technology to determine mental architecture and stopping rules. Comparison of the single versus double target conditions allows capacity analyses that strongly reinforce the double target factorial phase of the investigation. The results provide decisive support for parallel channels with either a self-terminating stopping rule or a coactive summation of information. General serial models and any variety of exhaustive processing were conclusively falsified.

Plasma passivation of gallium arsenide*

Improved electrical properties of the SiO2–GaAs interface have been obtained using in situ plasma surface treatments prior to film deposition. We present a comparison of several hydrogen based plasma passivation schemes: H2, H2/N2, and H2S. Hydrogen plasmas remove native oxides, while nitrogen or sulfur form passivating surface layers. Samples were characterized using metal–insulator–semiconductor C–V analysis, x-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry. The H2/N2 and H2S treated samples display improved C–V characteristics. XPS indicates the presence of nitrogen and sulfur respectively on the uncapped samples, although little evidence remains after SiO2 deposition. H2S plasmas offer the best results, providing a self-terminating process that prevents roughening of the GaAs surface by hydrogen plasma etching. However, surfaec doping effects were observed after exposure to high temperatures.

Localized electrodeposition induced by Joule heat at a constriction

We report a novel localized electrodeposition process based on localized Joule heating at a constriction and the temperature dependence of the equilibrium potential at a metal-electrolyte interface. Assuming a local temperature rise of 50 K, a deposition rate as high as 2 μm per minute of copper is theoretically predicted in acidified copper sulfate solution, which is verified by a series of experiments. Scanning electron microscopy micrographs show that the deposited copper is dense and crystalline. As an immediate application of this novel phenomenon, a method of self-induced repair for incipient opens, i.e., a self-locating and self-terminating process to treat constrictions in circuits, is established.

Haptic processing of spatially distributed information.

A haptic search paradigm, adapted from Treisman and Gelade’s (1980) visual search tasks, was used as an initial step in addressing issues relevant to the development of models of human and machine haptic object processing. Texture and/or edge-orientation information were presented to multiple finger locations in disjunction (Experiment 1) and conjunction (Experiment 2) search tasks. In Experiment 3, subjects performed a difficult single-feature (orientation) search. Although the disjunction task could be interpreted with parallel or serial exhaustive models of haptic processing, subjects showed a shift toward serial self-terminating processing with the more complex and difficult tasks. These results indicate processing changes when features of texture and shape must be integrated. Given other converging evidence, texture may be a better candidate than edge orientation for early perceptual processing, with information being processed preattentively and in parallel.

Searching for Map Symbols: The Cognitive Processes

Map images can be used to solve spatial tasks by employing processes similar to those used when looking at a cartographic map. Information encoded from a map, however, may not necessarily be stored as an analogue image of the map. This is likely to be the case when a person encodes information from a map to be used for a particular task. An experiment was performed where subjects searched cartographic maps displayed on a monitor to determine if particular map symbols were present. Relationships between the reaction times and the number of symbols on the maps indicated that subjects who were viewing the maps were using a serial self-terminating search process. A similar experiment was conducted with subjects who encoded the information on maps into memory and then determined if particular map symbols had been on the memorized maps. Relationships between reaction times and the number of symbols on the memorized maps indicated that a parallel search process was used by the memory subjects. Error rates were m...

Étude psycho­physiologique de la reconnaissance à court terme d'image avec les potentiels lents cérébraux (onde P300)

Summary : Psychobiological study of image recognition with slow event related potentials (P300). The study of P300 waves during the acquisition and recognition of simple symbolic pictures shows self-terminating processing in visual short-term memory. The observed data support a generai principle of psychobiological economy and the reduction of mental load. This principle is at variance with one of the postulates of Sternberg's additive factors theory. On the basis of the results a chronometry of the mental processes involved in visual short-term memory is proposed. Key words : event related potentials, P300, image recognition.

Shifting Ear Differences in Melody Comparison Through Transposition

Nonmusicians were required to classify pairs of melodies as “same” or “different”. When they were instructed to compare melodies played at the same pitch level as fast as possible, a REA was elicited. In contrast, a tendency in favor of the left ear came out when, all other things being equal, melodies were transposed, i.e. played at a different pitch level. Transposition was thus instrumental in leading subjects to rely more on right-hemisphere processing. Independent evidence for a change in the processing mode that whas adopted with these two types of material was provided by the response times. The results indicated the use of a selfterminating process of analytic search only with the untransposed melodies. Results are discussed in terms of the notion that the preferential use of local or global properties in melodies determines the intervention of the left or the right cerebral hemisphere, respectively.

Consistency checking in hypothesis generation

Three experiments were performed to study an aspect of a hypothesis-generation model. This model assumes a candidate hypothesis may be retrieved or activated in memory in response to only part of the available data. This candidate hypothesis may then be checked for consistency against the remaining data. The latter process is called “consistency checking.” Experiment 1 was performed to provide evidence that consistency checking occurs during hypothesis generation. Subjects were able to recognize hypotheses which were retrieved during a hypotheses-generation problem but not emitted as hypothesis responses, suggesting that consistency checking was responsible for the rejected hypotheses. Experiment 2 indicated that the amount of time needed to process an additional datum is a consistency-checking task was less than an estimate of the time needed to process an additional datum in hypothesis retrieval. The results suggest that consistency checking is a high-speed verification process rather than a slower search process. Experiment 3 was performed to provide evidence that consistency checking is a self-terminating process. Subjects' latencies depended upon the position of a disconfirming datum within a data set, supporting this conjecture. The results generally confirmed the existence of a high-speed verification process in hypothesis generation and also suggest that the generation of hypotheses in response to multiple data occurs as a result of dual processes.

Response latencies in discriminations of recency.

Subjects were asked to report which of two test words had been presented more recently in a list of 4 or 10 words. In each of four experiments, the study position of the probe that had been presented earlier in the list had little or no effect on response latency, whereas the study position of the probe that had been presented later in the list had a large and reliable effect on response latency. In Experiment 4, some test items were lures, and they had no effect on response latency. These results are incompatible with several theories of recency discrimination and strongly suggest parallel self-terminating processing of the probes.

Some evidence for a limited capacity parallel selfterminating process in simple visual search tasks

An experiment was carried out in order to investigate the questions of exhaustive vs selfterminating and serial vs parallel processing in a simple visual search task. In the experiment, 1, 2 or 3 letters were placed on an imaginary circle round the fixation point. Two different letters were used, one of which was defined as the ‘signal’. Ss had to respond ‘yes’ when one or more signals were in the display, ‘no’ otherwise. The number of signals in the display was varied from ‘no signals’ to ‘all signals’. A decrease in latencies with increasing number of signals for a fixed number of elements presented was observed indicating a selfterminating search. A decrease in latencies with increasing number of elements when only signals were presented was taken as evidence for a parallel selfterminating process. A further analysis of the error data showed that a limited capacity system had to be assumed. It was shown that it was possible to construct the overall pattern of latencies over conditions from the error data obtained.

反復試行に伴う同異反応時間の変化と情報処理特性

“Same-different” responses to arrays cosisting of 2 rows of 1, 3, 5, and 7 colored alpha-numerics were observed over 8 sessions of a four-week period with respect to whether every pair of the upper and lower items had the same attribute of either class (letter and digit) or color (red and blue). In the class attribute, the relation between the number of item-pairs (N) and reaction time (RT) was linear in every condition, and slopes for “same” were 275 msec in 1-2 sessions and 219 msec in 7-8 sessions, while those for “different” were 165 and 112 msec, respectively. These findings supported the hypothesis of the serial self-terminating processing of spatial information from class attribute, though the practice accelerated the processing rates to some extent. In the color attribute, difference between “same” and “different” RTs was not found, and RTs and N were almost independent with each other in 7-8 sessions, though the slope of N-RT function was still significant in early sessions. These suggested that spatial information from color attribute was essentially processed in parallel mode, and the practice had an effect to eliminate some nonessential operations accompanied in early sessions.

Some evidence for a selfterminating process in simple visual search tasks

Two experiments were conducted to investigate the unsettled question of whether the visual search process is selfterminating or exhaustive. In the experiments three letters were placed on an imaginary circle round the fixation point. Two different letters were used, one of which was defined as the ‘signal’. Ss had to respond ‘yes’ when one or more signals were in the display, ‘no’ otherwise. In both experiments the number of signals in the display was varied from 0 to 3. Decreasing latencies with increasing number of signals were observed in both experiments, indicating a selfterminating visual search. In experiment 1 a significant increase in latencies with increasing visual angle was found, in experiment 2 an increase in latency resulting from neighbouring contours. Both factors probably contribute to the slope of the function relating positive responses to display size and to the slope of the function relating negative responses to display size when stimuli are presented in linear arrays as in the experiment by Atkinson et al. (1969). As a result the slopes become more equal, falsely suggesting an exhaustive visual search process.

On the nature of central processing in choice reactions

A procedure for generating values of central processing uncertainty was developed from positive response data in a varied-set version of the Sternberg choice reaction task. This is a logical extension of a previously validated procedure for data from a fixed-set version of the same task. Both procedures provide information on the additive components of reaction time. It was concluded that S resolves more uncertainty in the varied-set than in the fixed-set situation. It was concluded also that S performs a rechecking operation prior to emitting a negative response, and this rechecking apparently involves less information than does the original testing for stimulus classification. This, in turn, suggests that rechecking is a self-terminating process with regard to display information. The results also imply that stimulus classification is partially serial and partially parallel, so a hybrid model may be appropriate for this task.