A feature-segmentation model of short-term visual memory

A feature-segmentation model of short-term visual memory (STVM) for contours is proposed. Memory of the First stimulus is maintained until the second stimulus is observed. Three processes interact to determine the relationship between stimulus and response: feature encoding, memory, and decision. Basic assumptions of the model are twofold: (i) the STVM system divides a contour into convex parts at regions of concavity; and (ii) the value of each convex part represented in STVM is an independent Gaussian random variable. Simulation showed that the five-parameter fits give a good account of the effects of the four experimental variables. The model provides evidence that: (i) contours are successfully encoded within 0.5 s exposure, regardless of pattern complexity; (ii) memory noise increases as a linear function of retention interval; (iii) the capacity of STVM, defined by pattern complexity (the degree that a pattern can be handled for several seconds with little loss), is about 4 convex parts; and (iv) the confusability contributing to the decision process is a primary factor in deteriorating recognition of complex figures. It is concluded that visually presented patterns can be retained in STVM with considerable precision for prolonged periods of time, though some loss of precision is inevitable.     

Low income, unemployment, and suicide mortality rates for middle-age persons in Japan

The relationships between age-specific suicide mortality rates and social life factors for all 47 Japanese prefectures in 1980, 1985, and 1990 were assessed by multiple regression analysis after factor analysis on 20 social life indicators. During this period, Japan experienced a secondary oil crisis in 1980-1983 and a bubble economy in 1986-1990. It was concluded that (1) low income was the major determinant which positively affected suicide mortality rate in middle-aged men during a previous 20-yr. period (1970-1990), (2) urbanization was negatively associated with male suicide mortality rates in most of the age classes in the 1980s, (3) unemployment was one of the major determinants of increased suicide mortality rate in middle-age men in the 1980s, and (4) unemployment was the major factor which was inversely associated with suicide mortality rate for elderly women from 1980 to 1990 in Japan.     

Effects of excitotoxic brain lesions on taste-mediated odor learning in the rat

The association learning between taste and odor is important in ingestive behavior. For a better understanding of this learning, we have developed a convenient and useful paradigm to assess the taste-mediated odor learning. In the training session, Wistar male rats drank water from two bottles in their home cages and from eight small glass dishes. In the learning session they were exposed in their home cages and also in a circular open-field apparatus to 0.005 M Na-saccharin and 0.02 M quinine hydrochloride which contained either banana or almond odors. One learning trial consisted of this pair of exposures. The preceding behavioral experiment has shown that these two odors are not aversive and are differentially perceived by rats. In the test session, the animals were put in the open-field apparatus equipped with eight dishes: four contained water with banana, and another four, with almond. Normal control rats preferred to drink water with the odor previously associated with saccharin. Stronger and more persistent preference was attained after two or three learning trials. To elucidate the brain sites responsible for this taste-mediated odor learning, the same procedure was assessed on brain-lesioned rats. Rats with lesions in the amygdala showed rapid extinction of preference to the saccharin-associated odor, whereas control rats did not. However, rats with lesions in the insular cortex showed retention of learning similar to that of the control rats. Rats with lesions in the sulcal prefrontal or cingulate cortices showed moderate disruptive effects on preference to the saccharin-associated odor. In conclusion, the odor learning established in our experimental paradigm is based on the association between the quality of odor and hedonics of taste. The amygdala may play a role in the formation, at least in the retention process, of this taste-odor association learning.     

Limited capacity for contour curvature in iconic memory

We measured the difference threshold for contour curvature in iconic memory by using the cued discrimination method. The study stimulus consisting of 2 to 6 curved contours was briefly presented in the fovea, followed by two lines as cues. Subjects discriminated the curvature of two cued curves. The cue delays were 0 msec. and 300 msec. in Exps. 1 and 2, respectively, and 50 msec. before the study offset in Exp. 3. Analysis of data from Exps. 1 and 2 showed that the Weber fraction rose monotonically with the increase in set size. Clear set-size effects indicate that iconic memory has a limited capacity. Moreover, clear set-size effect in Exp. 3 indicates that perception itself has a limited capacity. Larger set-size effects in Exp. 1 than in Exp. 3 suggest that iconic memory after perceptual process has limited capacity. These properties of iconic memory at threshold level are contradictory to the traditional view that iconic memory has a high capacity both at suprathreshold and categorical levels.     

Effect of applied stress on precipitation of Guinier–Preston zones in a Cu–0.9 wt.% Be single crystal

A stress-oriented formation of plate-shaped Guinier–Preston (GP) zones in single crystals of a Cu–0.9?wt.%?Be alloy aged at 200°C has been found. A compressive stress applied in the [001] direction assists the formation of the GP zones perpendicular to the [001] axis, while a tensile stress results in the preferential formation of the GP zones parallel to the stress axis. The applied stress strongly affects the nucleation of the GP zones. Free ageing at 275°C after compressive-stress ageing at 200°C produces plate-shaped γ′′ precipitates perpendicular to the stress axis, indicating a continuous change in the structure of the GP zones into that of the γ′′ phase. From length-change measurements during ageing, the misfit strains of the GP zone or γ′′ precipitate in directions parallel and perpendicular to the plate plane are estimated, respectively, as ?0.01 and ?0.10 for the GP zone and ?0.01 and ?0.11 for the γ′′ precipitate.     

Temperature dependence of the low-cycle fatigue behaviour of a Cu-SiO2 bicrystal with a [011], 18° twist boundary

The temperature dependence of the low-cycle fatigue behaviour of a Cu bicrystal containing dispersed SiO₂ particles and having a [011], 18° twist boundary has been studied. Failure occurred at shorter times with increasing temperature and stress amplitude. Crack nucleation took place at the particles' surfaces on the grain boundary where slip lines intersected. The crack tended to propagate along primary slip lines and this tendency became stronger as the temperature was increased.     

Short-term visual memory for contour curvature in a delayed discrimination task

Abstract: A two-interval forced-choice of constant stimuli was used to measure the point of subjective equality (PSE) and discrimination threshold for standard contour curvature (1.91, 3.24 deg⁻¹) held in short-term visual memory (STVM). At both standard curvatures, the PSE for remembered curvature was nearly constant for standard curvature from 2 s to 16 s retention intervals, while the discrimination threshold increased as a linear function of retention interval. These results show that the decay in STVM for contour curvature is due to the noisy representation of curvature, neither to fading of the represented curvature nor to converging to the constant curvature. Furthermore, the Weber fraction was nearly constant for both standard curvatures at any delay from 2 to 16 s.     

Strong interactions between hydrogen in solid solution and stress-induced martensite transformation of Ni–Ti superelastic alloy

The role of the dynamic interactions between hydrogen in a solid solution and the stress-induced martensite transformation in hydrogen embrittlement has been investigated using trained Ni–Ti superelastic alloy. In a cyclic tensile test in the stress plateau region caused by stress-induced martensite and reverse transformations after hydrogen charging, a further decrease in the critical stress for the martensite transformation is observed. In addition, the number of cycles to fracture for a trained specimen is significantly larger than that for a non-trained specimen. Since most of the charged hydrogen is preferentially trapped in defects induced by training, the hydrogen embrittlement is considerably suppressed as a result of decreasing interactions between the hydrogen and the transformation. The present results indicate that hydrogen in a solid solution more strongly interacts with the stress-induced martensite transformation than hydrogen trapped in defects, thereby further enhancing the hydrogen embrittlement related to phase transformations.     

Parenting and marital trust in Japan

This study examined the relationship between marital trust, mothers' parenting stress and maladjusted parenting behavior in Japan. The participants consisted of 327 Japanese mothers who reside in the greater Tokyo area and whose children go to kindergarten or nursery school (the children's ages range from 3 to 6 years. Participants were asked to complete questionnaires about their family structure (nuclear or extended family), demographic information about their child (sex, age, birth order. etc.), marital trust, parenting stress, and maladjusted childrearing behavior. Analysis indicated that the relationship between marital trust, mothers' parenting stress and maladjusted childrearing behavior was different depending on the family structure. More specifically, for mothers in nuclear families, marital trust, especially the sense of being trusted by the husband, was associated with parenting behavior directly as well as indirectly via parenting stress. In contrast, for mothers in an extended family marital trust was not associated with maternal parenting behavior. The results were discussed in terms of the differences in the availability of social support in a nuclear family compared to the extended family.     

Strain-induced submicrocrystalline grains developed in austenitic stainless steel under severe warm deformation

Strain-induced grain evolution in a 304 type austenitic stainless steel has been studied in multiple compression with the loading direction being changed in each pass. The tests were carried out to total strains above 6 at 873 K (0.5 T _m) at a strain rate of about 10^-3 s^-1. Multiple deformation promotes the rapid formation of many mutually crossing subboundaries because various slip systems operate from pass to pass. The gradual rise in misorientations across dislocation subboundaries with increasing strain finally leads to the evolution of very fine grains with large-angle boundaries. It is concluded that a new grained structure can result from a kind of continuous reaction during deformation, namely continuous dynamic recrystallization. Such deformation-induced grains are characterized by relatively low densities of dislocations, and considerable lattice curvatures developed in their interiors. The latter observations suggest that high elastic distortions are developed in the grain interiors and so such strain-induced grain structures are in a non-equilibrium state.