Showing papers on "Artifact (error) published in 1976"

Apparatus and process for producing artifact effect on sphygmometric information

Abstract: Improved method and apparatus for indicating blood pressure and the like in a varied pressure cuff system wherein blood vessel pulsation signals are supplied to signal processing means for determining the blood pressure. The blood pressure pulsations are monitored to detect artifacts and the signal processing means inhibited if an artifact is detected. Upon detection of an artifact the pressure applied by the cuff is automatically adjusted to repeat the pressure at which the artifact is detected, thereby to seek artifact-free values. The pressure-repetition may be a discrete pressure or a limited pressure range. Further, a maximum number of limited-pressure repetitions may be established, after which the entire pressure range must be repeated.

Elastic band artifact.

Abstract: Boy aged 2 History: Born in Bangladesh and came to UK at age of 3 months. * Seen in outpatient clinic with six-month history of a lesion around the neck described as beginning with a few spots which became confluent and discharged pus at intervals. His mother said he had difficulty in swallowing. On examination: Healthy except for hypertrophic scar completely encircling neck and from which beads of pus discharged (Fig 1). Cervical and occipital lymph nodes enlarged. He was apyrexial. Investigations: Chest and neck X-ray negative. Culture of pus negative. Management: It was felt that artifact was a likely cause and the lesion was surgically explored (J P S T) under general anasthetic. An elastic band (Fig 2) was found 8 mm beneath the skin surface. This was removed completely through five separate incisions. The patient made an uneventful recovery (Fig 3). The parents denied knowledge of the elastic band but did say that symptoms started when a number of families were living in the same house and the children had little supervision.

Pictures of the Past: Artifact Density and Computer Graphics

Abstract: The excavation of the site of a colonial fort produced a large quantity of artifacts but little else. The only data acquired were about artifact type and location of find. A computer was used to draw maps of various combinations of artifact distributions. Methods were borrowed from the engineering discipline of Image Processing in order to facilitate site interpretation. The implications of this are discussed in detail and its use demonstrated by the display of computer-produced isometric plots of artifact density over the excavation area.

"EAR" artifact in brain scans.

Abstract: The ear closest to the camera may be imaged in high-resolution lateral views of the brain as a structure anterior to the lateral sinus. The artifact can usually be eliminated by taping the auricle down. Artifacts such as this can be expected to become somewhat more of a problem as image resolution improves.

The Practice and Explanation of Coups D'Etat: Measurement or Artifact?

Abstract: A recent attempt in this Journal to explain \"coup activity\" during the 1960s in sub-Saharan African nations (Alan Wells, \"The Coup d'Etat in Theory and Practice: Independent Black Africa in the 1960s,\" AIJS 79 [January 1974]: 871-87) is methodologically weak and needs qualification. The validity of the suggested explanation based on the statistical analysis of aggregate data for these nations has to be seriously questioned, because (1) no attention is paid to the reliability of these data and (2) the data and the statistical analysis have no clear relationship to a coherent heoretical argument. Since information comparable to that used by Wells had been published for all but one of the countries he analyzes (Morrison et al. 1972), reliability estimates for his data could and should have been calculated. Although Wells never clearly operationalizes his basic terms (\"coups,\" \"aborted coups,\" and \"plots\"), it is reasonable to assume that such definitions would not diverge substantially from those in Morrison et al. (1972, chap. 12). In table 1, the frequency counts of these events as coded by Wells and by Morrison and Stevenson (1971) and Morrison et al. (1972) are presented, along with a variety of indices which combine these counts into a single scale. Wells's index of coup activity weights the frequency of each type of event and then standardizes the sum by the number of years since 1960 or since independence, if that occurred after 1960. We calculated indices for both data sets, and in addition we present a previously published \"eliteinstability\" index, using weights different from those used by Wells but using the same variables. This latter index is calculated both with and without standardization for the period since independence. The reliability coefficients for the interindex comparisons are shown in table 2. These coefficients demonstrate moderately high intercoder agreement as well as an apparent irrelevance of differences between Wells's weighting and standardization procedures and those described in Morrison and Stevenson (1971). Nevertheless, the differences in the raw event codings need some explanation. First, it is apparent from table 1 that Wells consistently reports comparatively fewer plots and more aborted coups. The reasons for this cannot be inferred from the data as presented, however. Second, there are some significant differences inthe codings of coups d'etat: by our count there were two coups in Nigeria, both in 1966 (Wells had four); one coup (not two) in the Sudan, since the events of 1964 seem to reflect a mass revolt rather than a coup d'etat; a coup in Uganda (Wells

Medium for External Acoustic Transmission

Abstract: The transducer-skin interface artifact makes single crystal, sector-scanner and multicrystal echocardiographic assessment of anterior cardiac structures technically more difficult than posterior structure evaluation. Furthermore, because of transducer fulcrum effect (pie wedge), relatively less area of the anterior heart can be evaluated with standard single crystal echocardiography during a sweep or with use of sector-scanners. In smaller children, further problems exist with two dimensional instruments. These include the sector-scanner transducer vibrations which might frighten children and loss of transducer-skin contact with small degrees of transducer angulation from multicrystal instruments.

Qualitative And Quantitative Artifact From CT Algorithms

Abstract: Image artifacts in computed tomography originate either in the hardware or software components of the system. Software artifacts may be classified as qualitative or quantitative depending, respectively, upon whether the rms artifact converges within the image field or whether it diverges. As an example of quantitative artifact, we demonstrate that truncated algorithms, often recommended for reducing reconstruction time, inherently generate aperature-error or size-effect artifact. As an example of qualitative artifact, we demonstrate that algorithms giving sharpest edge-definition do not yield generally superior point resolution. These "sharp" algorithms, however, do generate large qualitative artifact, and require relatively long computer time. Prereconstruction and postreconstruction averaging, often introduced to alleviate noise and artifact problems, can be eliminated completely. One achieves the same final result by initially choosing a different, and often simpler, reconstruction convolution.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Respiratory evoked potentials of the cerebral cortex associated with speech production

Abstract: Scalp-recorded cortical potentials of four subjects were recorded from temporofrontal and central areas during speech and control tasks. Computer averaging of the brain potentials was carried out with respect to onset of inspira­ tion and onset of phonation to determine if respiratbryrelated potentials could have been a contaminating factor in previously reported pre-speech potentials. Eye artifact contributed significantly to summated averages of the BEG responses, and no pre-speech or pre-respiration potentials were found. Results were discussed in terms.of whether or not it is possible to eliminate ocular artifact from EEC . responses recorded during speech.

Potential artifact in dichoptic backward masking.

Abstract: Under some conditions a dark interval in the target eye may be concomitant with presentation of a dichoptic mask. Results show that this monoptic dark interval contributes to the over-all observed dichoptic masking effect.