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At least 343 records · Page 19Linked to original sources
PubMed1989

Component analysis of spatial and spectral patterns in multispectral images. II. Entropy minimization.

In Part I [J. Opt. Soc. Am. A 4, 2101 (1987)] of this series, we developed a method for estimating both spatial patterns and spectral curves of components in a multispectral scene. This method does not need spatial and spectral information about the components but only multispread imagery data. The estimation is given as a feasible solution set satisfying the nonnegativity constraint for density and spectral response for all components at all pixels. In this paper, we estimate unique solutions for both the component patterns and the spectra from the feasible solution set. The solution is given by optimizing an entropy minimization criterion. This criterion enhances the spectral or spatial features of individual components. Two experimental results are shown to demonstrate the effectiveness of this method with biological and cytochemical specimens. The limitations of this method for unique pattern estimation are also discussed.

Algorithms↗
PubMed2000

[Hospital system as a source of information to estimate stillbirth and neonatal mortality rates].

OBJECTIVE: Studies on the evolution of infant mortality rate are very relevant. Nevertheless, lack of vital statistics in Brazil limits the temporal and spatial analysis of this indicator. This study aims to investigate the possible use of the Brazilian Hospital Information System as an alternative information source for stillbirth and neonatal mortality rates by age group. METHODS: A new method to estimate the stillbirth and neonatal mortality rates is proposed. It was applied in a set of selected Brazilian states in the year of 1995. For comparative purposes, the Brazilian Death Information System was assessed to estimate the mortality rates under study, after adjusting the registered number of live births by using a demographic tool. RESULTS: By assessing the Hospital Information System a larger number of fetal and early neonatal deaths were observed when compared to data given by the death information system of the Northeastern states. Besides, in the Southern and Southeastern states, where death records are more thorough, the mortality rates calculated using both information sources were very similar. CONCLUSIONS: The results suggest that the proposed methodology could greatly contribute to the analysis of the spatial-time evolution of stillbirth and neonatal death rates in recent years in Brazil, as data on death registration in the majority of the Brazilian states are less thorough than those from the hospital information system.

Brazil↗
PubMed1995

[Interrelationship between the facial expression and familiarity: analysis using spatial filtering and inverted presentation].

We investigated interrelationship between the facial expression and familiarity using spatial filtering and inverted presentation. The stimuli were facial images (smiling and neutral faces) band-pass filtered in the spatial domain. If the filtering is carried out at low spatial frequencies, the images convey more global features than the local ones, whereas the local features are emphasized in the images filtered at high frequencies. The task of subjects was to judge the expression (Experiment 1) or familiarity (Experiment 2) of such images, which were presented in the upright or inverted orientation. The following results were obtained. 1) Spatial frequency components in the middle range (12.4 and 24.8 cycles/face-width) were important in recognizing both expression and familiarity, 2) there was close relationship between the facial expression and familiarity, and 3) smiling faces were harder to recognize when they are shown in the inverted orientation. These results suggest that there are the common and different recognition processes between facial expression and familiarity.

Adult↗
PubMed1999

EEG topographical analysis of spatial disorientation.

BACKGROUND: We examined EEG topography while subjects experienced spatial disorientation (SD) such as vection and somatogravic illusion (SGI). METHODS: Five healthy male subjects were exposed to a rotating image evoking vection (Experiment 1) and to a 0.58 G linear forward acceleration evoking SGI (Experiment 2). The data were analog-to-digital converted with an epoch length of 1 s and a sampling frequency of 256 Hz. Polynomial coefficient vectors were calculated for the following analyses of EEG under the illusion: a) objective evaluation of topographical difference by two-way MANOVA; b) visual inspection of the power spectra maps; and c) logarithmic deviation ratio topography (log DRT). RESULTS: MANOVA demonstrated significant differences in EEG topography in the high alpha band while the vection was evoked. No significant difference was revealed in any bands for SGI. Characteristic patterns common to all subjects were hardly identified on the power spectra maps. By log DRT under vection, a decrease of power was observed in the centro-parietal area on the left side in one subject, on the right in another subject, and in the mid-right frontal area in a third subject compared with the control with eyes open. As for SGI, log DRT revealed a decrease of power in the occipital area in most of the trials as the magnitude was reduced by a visible horizon. CONCLUSIONS: MANOVA revealed a significant change in EEG topography while the subjects felt vection. Log DRT reflected characteristic patterns under vection and SGI. Thus EEG topography may be useful for the study of SD.

Acceleration↗
PubMed2000

[Geostatistical analysis on spatial patterns of Aphis gossypii and Propylaca japonica].

The spatial construction and distribution of Aphis gossypii and Propylaca japonica at different period were investigated with geostatistics. The results showed that the semivariogram of Aphis gossypii was described by spherical model, indicating an aggregated spatial arrangement, the range was 8.21-10.81 m. The semivariograms of Propylaca japonica was fitted by spherical model too, also indicating an aggregated spatial arrangement, its range was 8.01-14.25 m. The amount and spatial distribution of Propylaca japonica was closely related to that of Aphis gossypii. It reveals that Propylaca japonica is dominant natural enemies of influencing population of Ahphis gossypii.

Animals↗