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At least 91 records · Page 5Linked to original sources
PubMed1976

High reliability rates of spatial pattern analysis by vectorcardiogram in assessing the severity of eccentric left ventricular hypertrophy.

In 33 patients, including 12 control subjects and 21 with eccentric LVH, LV mass determined by angiocardiogram was correlated to 26 VCG measurements (Frank system) calculated from the scalar X, Y, and Z leads. The results demonstrated that the most reliable indices of VCG in assessing the severity of eccentric LVH determined by angiocardiogram were the magnitude of the spatial mean QRS vector and the time of the spatial maximal QRS vector ("spatial VAT"), of which correlation coefficients were 0.93 and 0.93, respectively. Such high correlation coefficients have never been obtained with the usual ECG analysis. These findings strongly suggest that (1) increased QRS voltage and usual prolonged QRS duration in eccentric LVH are due to an increase in LV mass, and (2) prolonged VAT observed in eccentric LVH is closely related to an anatomic alteration, namely, the greater distance of intra-ventricular conducting pathways as the result of LV dilatation, as an increase in LV mass is usually paralleled by the grade of the chamber enlargement in this type of LVH. Regarding the T loop, correlations between the LV mass and the VCG measurements were less as compared to those of the QRS loop. In general, T changes in moderate or severe LVH may be also related to a certain altered cardiac muscle state, in addition to an increase in LV mass. Angiocardiographic and light microscopic findings of a patient with eccentric LVH in whom a widened QRS-T angle was demonstrated to an extent much more than that expected with an increase in LV mass are presented and discussed. The spatial pattern analysis by VCG is very useful and reliable in assessing the severity of eccentric LVH.

Adolescent↗
PubMed1981

Spatial kinematic analysis of the upper extremity using a biplanar videotaping method.

A biplanar videotaping system is used to generate spatial kinematic data of an upper extremity motion. The technique is based upon the characterization of each segment by four points in three-dimensional space using biplanar videotaping and subsequent analysis by computer-aided descriptive geometry. The tests were conducted to determine the system's accuracy and repeatability. The results of the joint kinematics of the test subjects performing a diagonal reaching activity with and without an orthosis (or an assistive device) are presented.

Biomechanical Phenomena↗
PubMedDate not supplied

[Etiology, occurrence and types of the internal carotid artery loop].

Internal carotid loop was studied in 99 patients out of 1638 cases subjected to angiography. The presence of a loop was arbitrarily accepted when in the tortuous part of the artery one of its segments was situated below the preceding segment. For the spatial analysis of the tortuous part of the artery and its image in the plane of the radiogram a model was used simulating various variants of the course of the internal carotid artery. On the ground of the analysis of the spatial configuration of the arterial loops and the variability of the loop model in the plane of the radiogram six types of the loop were isolated. The loops were found in 9.2% of patients with bilateral angiography and 5.7% of those with unilateral angiography. In adults the loop was present in 5.4% of cases, and in children in 8.9% (statistically significant difference p less than 0.05). It is assumed that the loop in children is a congenital anomaly, while in adulthood besides the congenital etiology an acquired form of the loop is to be taken into account.

Adolescent↗
PubMed1981

Cortical anatomy, size invariance, and spatial frequency analysis.

In a recent application of an algorithm developed in computer and optical pattern recognition, Cavanagh has suggested that a composite of spatial frequency mapping and complex logarithmic mapping would provide translationally, rotationally, and size-invariant mechanism for human vision. In this work, Cavanagh has not made explicit the fact that this transformation is composite, that is, that the first step (global Fourier analysis) perceptually, anatomically, and physiologically inconsistent with primate vision, but that the second step (complex logarithmic mapping) is actually embodied in the anatomy of the primate retinostriate projection. Moreover, it is the complex logarithmic remapping step which is entirely responsible for the computational simplification of the symmetries of size and rotation invariance. These facts, which have been extensively discussed in a recent series of papers, are briefly reviewed and illustrated. Furthermore, it is shown that the architecture of the retinostriate map may provide an example of computational anatomy in vision, such that the spatial representation of a stimulus in the brain may be of direct functional significance to perception, and to the nature of certain visual illusions.

Afterimage↗
PubMed1986

Event-related potentials of the brain and cognitive processes: approaches and applications.

Event-related potentials (ERPs) are recordings of the electric field which the brain produces in fixed time-relation to an event. ERPs open a time and space window onto covert steps of brain information processing which need not be accompanied by overt behavior or private experiences. ERPs are the only noninvasive method which resolves the dynamic pattern of events in the human brain down to the millisecond range. Early ERP components are valuable tools in clinical testing of the afferent sensory systems in the absence of anamnestic or clinical pathology. Later components (e.g. the 'P300') index intermediate, covert steps of information processing and have clarified the time course and the contingencies of processes in attention, decisions and language. ERP waveshapes show electric potential differences between two recording points. Conventional analysis often ignores the fact that there is no unique voltage amplitude or signal latency for a single point, and interprets ambiguous results. Although important insights have emerged with such strategies, full utilization of ERP data requires unambiguous ERP assessment and converging evidence from neuropsychological and cognitive experimentation. Sequences of field distribution maps offer an unbiased display of ERP data. Spatial analysis yields unambiguous values for further comprehensive assessment, and should precede analysis over time. Examples of spatial analysis have shown that different ERP field configurations follow the presentation of noun and verb meaning of homophone words; that the ERP effects to subjective contours resemble those to attention in time course and topography; that the 'cognitive' P300 component reflects the specific stimulus location; and that subliminal information influences the configuration of late ERP fields.

Attention↗
PubMed1981

A variance components approach to categorical data models with heterogeneous cell populations: analysis of spatial gradients in lung cancer mortality rates in North Carolina counties.

A mixed categorical-continuous variable model is proposed for the analysis of mortality rates. This model differs from other available models, such as weighted least squares and loglinear models, in that the within-cell populations are assumed to be heterogeneous in their levels of mortality risk. Heterogeneity implies that, in addition to the sampling variance considered in other available models, there will be a second component of variance due solely to within-cell heterogeneity. Maximum likelihood procedures are presented for the estimation of the model parameters. These procedures are based on the assumption that the distribution function for each cell death count is the negative binomial probability function. This assumption is shown to be equivalent to assuming a mixture of Poisson processes with the differential risk levels among individuals within each cell being governed by a two-parameter gamma distribution. The model is applied to data on lung cancer mortality for 1970-1975 for the 100 counties of North Carolina. The analysis shows that, though a gradient in lung cancer mortality rates exist in space, the gradient is restricted to specific demographic categories identified by race, age and sex.

Adult↗
PubMed1980

Spatial frequency analysis in early visual processing.

The existence of multiple channels, or multiple receptive field sizes, in the visual system does not commit us to any particular theory of spatial encoding in vision. However, distortions of apparent spatial frequency and width in a wide variety of conditions favour the idea that each channel carries a width- or frequency-related code or 'label' rather than a 'local sign' or positional label. When distortions of spatial frequency occur without prior adaptation (e.g. at low contrast or low luminance) they are associated with lowered sensitivity, and may be due to a mismatch between the perceptual labels and the actual tuning of the channels. A low-level representation of retinal space could be constructed from the spatial information encoded by the channels, rather than being projected intact from the retina.

Form Perception↗
PubMed1995

A frequency domain analysis of spatial organization of epicardial maps.

Mapping of organized rhythms like sinus rhythm uses activation times from individual electrograms, and often assumes that the map for a single activation is similar to maps for subsequent activations. However, during fibrillation, activation times and electrograms are not easy to define, and maps change from activation to activation. Volume and complexity of data make analysis of more than a few seconds of fibrillation difficult. Magnitude Squared Coherence (MSC), a frequency domain measure of the phase consistency between two signals, can be used to help interpret longer data segments without defining activation times or electrograms. Sinus rhythm, flutter, and fibrillation in humans and swine were mapped with an array of unipolar electrodes (2.5 mm apart) at 240 sites on the atrial or ventricular epicardium. Four-second data segments were analyzed. One site near the center of the array was chosen ad hoc as a reference. MSC maps were made by measuring mean MSC from 0-50 Hz between every point in the array relative to the reference. Isocoherence contours were drawn. The effects of bias in the coherence estimate due to misalignment were investigated. Average MSC versus distance from the reference was measured for all rhythms. Results indicate that in a 4-s segment of fibrillation, there can exist some phase consistency between one site and the reference and little or none between a second site and the reference even when both sites are equidistant from the reference. In fibrillation, isocoherence contours are elongated and irregularly shaped, reflecting long-term, but nonuniform, spatial organization. That is, activation during fibrillation cannot be considered as random over a 4-s interval. Bias in the coherence estimate due to misalignment is significant for sinus rhythm and flutter, but can be corrected by manual realignment. Average MSC drops with distance for all rhythms, being most pronounced for fibrillation, MSC maps may provide insights into long-term spatial organization of rhythms that would otherwise be cumbersome and difficult to interpret with standard time domain analysis.

Animals↗
PubMed1991

Second-order analysis of spatial clustering for inhomogeneous populations.

Motivated by recent interest in the possible spatial clustering of rare diseases, the paper develops an approach to the assessment of spatial clustering based on the second-moment properties of a labelled point process. The concept of no spatial clustering is identified with the hypothesis that in a realisation of a stationary spatial point process consisting of events of two qualitatively different types, the type 1 events are a random sample from the superposition of type 1 and type 2 events. A diagnostic plot for estimating the nature and physical scale of clustering effects is proposed. The availability of Monte Carlo tests of significance is noted. An application to published data on the spatial distribution of childhood leukaemia and lymphoma in North Humberside is described.

Biometry↗
PubMed1986

High spatial resolution analysis using parallel detection eels.

The application of parallel detection electron energy loss spectroscopy to the characterization of small particles or interfaces is demonstrated. Data are presented that show variations of low energy loss plasmons, Al L23 edge near edge fine structure, and oxygen concentration with spatial resolution better than 10 nm. The use of this technique for chemical and electronic structure measurements from very small specimen volumes is discussed.

Microscopy, Electron↗
PubMed1991

Temporal analysis and spatial mapping of Lymantria dispar nuclear polyhedrosis virus transcripts and in vitro translation polypeptides.

Genomic expression of the Lymantria dispar multinucleocapsid nuclear polyhedrosis virus (LdMNPV) was studied. Viral specific transcripts expressed in cell culture at various times from 2 through 72 h postinfection were identified and their genomic origins mapped through Northern analysis. Sixty-five distinct transcripts were identified in this analysis. Most viral transcripts were expressed late in infection, and originated from throughout the viral genome. Viral polypeptides expressed in infected 652Y cells were labeled with [35S]methionine and identified by autoradiography after separation by SDS polyacrylamide gel electrophoresis. Viral protein synthesis was found to occur in a sequential manner. Four proteins were identified in the early phase of viral replication (4-12 h p.i.), 24 proteins in the intermediate phase (12-24 h p.i.), and 5 proteins during the late phase (greater than 24 h p.i.). Cytoplasmic RNAs were isolated from LdMNPV infected cells at 16, 24, and 48 h p.i., and used for hybrid selections with overlapping DNA fragments that covered the entire LdMNPV genome. The selected RNAs were translated in vitro, and 61 distinct viral polypeptides were identified and their genomic origins mapped. Temporal and spatial transcription and translation maps of the LdMNPV genome were generated with these data, and the expression pattern of the LdMNPV genome was compared to that of the Autographa californica nuclear polyhedrosis virus.

Animals↗
PubMed1989

Binocular interactions in the cat's dorsal lateral geniculate nucleus. I. Spatial-frequency analysis of responses of X, Y, and W cells to nondominant-eye stimulation.

1. X, Y, and W cells in the A and C layers of the cat's dorsal lateral geniculate nucleus (LGN) were tested for responses to stimulation of the nondominant eye. The main purpose was to determine the incidence of nondominant-eye excitation and inhibition among different classes of cells and to examine the spatial-frequency tuning of responses to the nondominant eye. 2. Of 198 cells that were tested with drifting sine-wave gratings presented to the nondominant eye, 109 (55%) showed statistically significant responses. Four types of responses were observed: an increase in the mean discharge rate (F0 excitation), a decrease in the mean discharge rate (F0 inhibition), an increased modulation at the fundamental frequency of the grating (F1 excitation), and a decreased modulation at the fundamental frequency of the grating (F1 inhibition). Overall, 29% of the cells responded with inhibition, 24% responded with excitation, and 2% showed both excitation and inhibition, depending upon the spatial frequency and/or the harmonic response component. The relative incidence of excitation and inhibition was similar for X, Y, and W cells, for cells with on-center and off-center receptive fields, for cells with different receptive-field eccentricities, and for cells in each LGN layer. In addition, within layers A and A1, responses were similar for cells at different distances from the laminar borders. 3. Spatial-frequency response functions indicated that cells could have band-pass or low-pass spatial-frequency tuning through the nondominant eye. Band-pass cells tended to be narrowly tuned (less than or equal to 1 octave), and low-pass cells responded to a broader range of spatial frequencies. These properties were similar for X, Y, and W cells. Spatial resolution tended to be low (less than or equal to 0.8 c/deg for most cells), although a few cells responded to the highest spatial frequency tested (5.4 c/deg). Likewise, optimal spatial frequency was low (less than or equal to 0.2 c/deg) for most cells. These properties were similar for X and Y cells, and there was a weak tendency for X and Y cells to have higher optimal spatial frequencies and spatial resolutions than W cells. 4. In terms of absolute change in activity, responses to drifting gratings were weak. However, cells that were inhibited generally showed 20-60% decreases in activity to the optimal spatial frequency, and cells that were excited generally showed 40-100% increases. Response amplitudes were similar for X, Y, and W cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1978

Stiffness gradient along the basilar membrane as a basis for spatial frequency analysis within the cochlea.

Stiffness z of the basilar membrane of the house mouse against a displacement by sound was calculated from data on width and thickness of the membrane. Three functions of the kind log10z = ax + b were obtained which equally express the stiffness change in dependence on the locus x on the basilar membrane. These functions were compared with the one for frequency representation. The result is that the spatial distribution of displacement maxima for frequencies and of stiffness follows the same kind of place-dependent functions over a large portion of the basilar membrane. From this it can be concluded empirically that the frequency and stiffness (calculated from width and thickness of the basilar membrane) scales along the cochlea are generally proportional to each other and that stiffness is a dominant factor for the determination of the locus of the displacement maximum for a given frequency.

Acoustic Stimulation↗
PubMed1992

Application of three-dimensional molecular hydrophobicity potential to the analysis of spatial organization of membrane domains in proteins: I. Hydrophobic properties of transmembrane segments of Na+, K(+)-ATPase.

A new computer-aided molecular modeling approach based on the concept of three-dimensional (3D) molecular hydrophobicity potential has been developed to calculate the spatial organization of intramembrane domains in proteins. The method has been tested by calculating the arrangement of membrane-spanning segments in the photoreaction center of Rhodopseudomonas viridis and comparing the results obtained with those derived from the X-ray data. We have applied this computational procedure to the analysis of interhelical packing in membrane moiety of Na+, K(+)-ATPase. The work consists of three parts. In Part I, 3D distributions of electrostatic and molecular hydrophobicity potentials on the surfaces of transmembrane helical peptides were computed and visualized. The hydrophobic and electrostatic properties of helices are discussed from the point of view of their possible arrangement within the protein molecule. Interlocation of helical segments connected with short extramembrane loops found by means of optimization of their hydrophobic/hydrophilic contacts is considered in Part II. The most probable 3D model of packing of helical peptides in the membrane domain of Na+, K(+)-ATPase is discussed in the final part of the work.

Amino Acid Sequence↗
PubMed1978

[Electrophysiological methods of assessing myocardial hypoxia].

The potentialitis of the standard electrocardiogram, precordial cartogram and spatial analysis are confronted in 38 patients with extensive anterior or anteroseptal myocardial infarction, acute phase, in order to determine the extent and propagation of the myocardial hypoxia. The determination is performed on the base of the correlation dependence as regards the creatinine-phosphokinase level in blood. The best degree of correlation dependence has the spatial analysis of the changes in the segment ST - Vmax ST sp. r=0.69, as well as the changes in the segment ST reflected in the precordial electrocardiography - nST-0.1 mv. r=0.67. Close is the degree of correlation dependence in the standard electrocardiogram - STv r=0.59. The difference in the correlation coefficients are not statistically significant, allowing their application in the routine work of the three methods.

Acute Disease↗
PubMed1992

Analysis of spatial structure of thymocytes and of their contacts with thymic non-lymphoid cells.

The study aimed et determining morphological relations between thymic cells and thymocytes. The studies were performed on 16 days old rats of Wistar strain. The material was processed for ultrastructural studies in a routine manner. For 50 thymocytes computer reconstruction was performed which allowed to define cell volume, volume of cell nucleus and of condensed chromatin. The value characterizing three-dimensional morphology of thymocytes provided grounds for analysis using graph theory. The stereological methods allowed to examine microarchitecture of individual thymic zones. Thymocytes in contact with dendritic cells or with macrophages were found to differ in morphology from thymocytes with no such contacts. The results indicated direct effect of dendritic cells and of macrophages on thymocytes.

Animals↗