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Visual Estimation (visual + estimation)
Selected AbstractsProglacial Sediment,Landform Associations of a Polythermal Glacier: Storglaciären, Northern SwedenGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2003James L. Etienne Abstract Mapping and laboratory analysis of the sediment,landform associations in the proglacial area of polythermal Storglaciären, Tarfala, northern Sweden, reveal six distinct lithofacies. Sandy gravel, silty gravel, massive sand and silty sand are interpreted as glaciofluvial in origin. A variable, pervasively deformed to massive clast-rich sandy diamicton is interpreted as the product of an actively deforming subglacial till layer. Massive block gravels, comprising two distinctive moraine ridges, reflect supraglacial sedimentation and ice-marginal and subglacial reworking of heterogeneous proglacial sediments during the Little Ice Age and an earlier more extensive advance. Visual estimation of the relative abundance of these lithofacies suggests that the sandy gravel lithofacies is of the most volumetric importance, followed by the diamicton and block gravels. Sedimentological analysis suggests that the role of a deforming basal till layer has been the dominant factor controlling glacier flow throughout the Little Ice Age, punctuated by shorter (warmer and wetter climatic) periods where high water pressures may have played a more important role. These results contribute to the database that facilitates discrimination of past glacier thermal regimes and dynamics in areas that are no longer glacierized, as well as older glaciations in the geological record. [source] The Pocket Echocardiograph: Validation and FeasibilityECHOCARDIOGRAPHY, Issue 7 2010Benjamin C. Culp M.D. Background: A new, miniaturized ultrasound device, the pocket echocardiograph (PE), is highly portable and can be carried inside a lab-coat pocket. Studies of this device are limited and have not examined the use by novice echocardiographers. We hypothesize that a novice echocardiographer can use PE to produce interpretable cardiac images, and that both novice and expert echocardiographers can use PE to accurately quantify ejection fraction. Methods: Unselected subjects (n = 40) in an echocardiography laboratory underwent blinded formal transthoracic echocardiography (TTE) and PE (Acuson P10, Siemens, Mountain View, CA, USA). A cardiology fellow with 2 months of echocardiography training acquired PE images. The fellow and an experienced echocardiographer interpreted the PE studies offline in a blinded fashion. To assess adequacy, studies were graded as technically adequate, limited, or inadequate. A visual estimation of ejection fraction was made. Comparisons were made to the formal reported TTE. Results: Subjects were heterogeneous, 43% male; age 64 ± 17 years, and ejection fraction 52.4%± 12.3%. All PE studies were interpretable, and the vast majority of PE and TTE images were considered technically adequate (77.5% and 85% respectively; P = 0.32). Ejection fraction showed a good correlation, bias, and limits of agreement for the fellow's interpretation (r = 0.78, ,5.9%, ±16.6%) with stronger association for the experienced echocardiographer (r = 0.88, ,0.8%, ±11.4%). Conclusion: Novice echocardiographers using the PE can produce adequate quality images. Both expert and novice echocardiographers can use PE to quantify ejection fraction over a broad range of patients. The device's low cost and portability may greatly expand the availability of bedside echocardiography for routine or urgent cardiovascular assessment. (Echocardiography 2010;27:759-764) [source] Visual Quantitative Estimation: Semiquantitative Wall Motion Scoring and Determination of Ejection FractionECHOCARDIOGRAPHY, Issue 5 2003M.D., Steven J. Lavine Ejection fraction (EF) is the most commonly used parameter of left ventricular (LV) systolic function and can be assessed by echocardiography. Quantitative echocardiography is time consuming and is as accurate as visual estimation, which has significant variability. We hypothesized that each echocardiographer has developed a mental set of guidelines that relate to how much individual segment shortening constitutes normal function or hypokinesis of varying extents. We determined the accuracy of applying these guidelines to an accepted technique of EF determination using a retrospective analysis of consecutive two-dimensional echocardiographic studies performed on patients who had radioventriculography (RVG) within 48 hours. Using a 12 segment model, we scored each segment at the base and mid-ventricular level based on segmental excursion and thickening. The apex was scored similarly but with 1/3 of the value based on a cylinder-cone model. EF was determined from the sum of segment scores and was estimated visually. We termed this approach visual quantitative estimation (VQE). We correlated the EF derived from VQE and visual estimation with RVG EF. In the training set, VQE demonstrated a strong correlation with RVG(r = 0.969), which was significantly greater than visual estimation(r = 0.896, P < 0.01). The limits of agreement for VQE (+12% to ,7%) were similar to the limits of RVG agreement with contrast ventriculography (+10% to ,11%) with similar intraobserver and interobserver variabilities. Similar correlation was noted in the prediction set between VQE and RVG EF(r = 0.967, P < 0.001). We conclude that VQE provides highly correlated estimates of EF with RVG. (ECHOCARDIOGRAPHY, Volume 20, July 2003) [source] High-density lipoprotein cholesterol, C-reactive protein, and prevalence and severity of coronary artery disease in 5641 consecutive patients undergoing coronary angiographyEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 6 2008H. F. Alber ABSTRACT Background, Although high-density lipoprotein cholesterol (HDL-C) and C-reactive protein (CRP) are well-established predictors for future cardiovascular events, little information is available regarding their correlation with the prevalence and severity of angiographically evaluated coronary artery disease (CAD). Material and methods,, Five thousand six hundred forty-one consecutive patients undergoing coronary angiography for the evaluation of CAD were analysed. Cardiovascular risk factors were assessed by routine blood chemistry and questionnaire. CAD severity was graded by visual estimation of lumen diameter stenosis with significant stenoses defined as lumen diameter reduction of , 70%. Coronary angiograms were graded as one-, two- or three-vessel disease, as nonsignificant CAD (lumen irregularities < 70%) or non-CAD. Results,, HDL-C (60·3 ± 18·5 vs. 51·9 ± 15·3 mg dL,1; P < 0·001) was higher and CRP was lower (0·65 ± 1·68 vs. 1·02 ± 2·38 mg dL,1; P < 0·001) in non-CAD (n = 1517) compared to overall CAD patients (n = 4124). CAD patients were older (65·2 ± 10·5 years vs. 59·9 ± 11·4 years), more often diabetics (19·2% vs. 10·6%) and hypertensives (79·2% vs. 66·0%) and included more smokers (18·8% vs. 16·5%) (all P < 0·005). Low-density lipoprotein cholesterol (124·5 ± 38·3 vs. 126·0 ± 36·3 mg dL,1; P = NS) was similar in overall CAD and non-CAD patients with more statin users (43·4% vs. 27·9%; P < 0·001) among CAD patients. Comparing non-CAD with different CAD severities using analysis of variance, results did not change substantially. In a multivariate analysis, HDL-C and CRP remained independently associated with the prevalence of CAD. In addition, HDL-C is also a potent predictor for the severity of CAD. Conclusions,, In this large consecutive patient cohort, HDL-C and CRP are independently associated with the prevalence of CAD. In this analysis, HDL-C is an even stronger predictor for CAD than some other major classical risk factors. [source] Computer-aided calibration for visual estimation of vegetation coverJOURNAL OF VEGETATION SCIENCE, Issue 6 2009Åsa Gallegos Torell Abstract Question: What precision and accuracy of visual cover estimations can be achieved after repeated calibration with images of vegetation in which the true cover is known, and what factors influence the results? Methods: Digital images were created, in which the true cover of vegetation was digitally calculated. Fifteen observers made repeated estimates with immediate feedback on the true cover. The effects on precision and accuracy through time were evaluated with repeated proficiency tests. In a field trial, cover estimates, before and after calibration, were compared with point frequency data. Results: Even a short time of calibration greatly improves precision and accuracy of the estimates, and can also reduce the influence of different backgrounds, aggregation patterns and experience. Experienced observers had a stronger tendency to underestimate the cover of narrow-leaved grasses before calibration. The field trial showed positive effects of computer-based calibration on precision, in that it led to considerably less between-observer variation for one of the two species groups. Conclusions: Computer-aided calibration of vegetation cover estimation is simple, self-explanatory and time-efficient, and might possibly reduce biases and drifts in estimate levels over time. Such calibration can also reduce between-observer variation in field estimates, at least for some species. However, the effects of calibration on estimations in the field must be further evaluated, especially for multilayered vegetation. [source] Effects of sampling teams and estimation methods on the assessment of plant coverJOURNAL OF VEGETATION SCIENCE, Issue 6 2003Suzanne M. Kercher Abstract. We evaluated variability in cover estimation data obtained by (1) two sampling teams who double sampled plots and (2) one team that used two methods (line intercepts and visual estimation of cover classes) to characterize vegetation of herbaceous wetlands. Species richness and cover estimates were similar among teams and among methods, but one sampling team scored cover higher than the other. The line intercept technique yielded higher cover estimates but lower species richness estimates than the cover class method. Cluster analyses of plots revealed that 36% and 11% of plots sampled consecutively by two teams or using two methods, respectively, were similar enough in species composition and abundance to be paired together in the resulting clustering tree. Simplifying cover estimate data to presence/absence increased the similarity among both teams and methods at the plot scale. Teams were very similar in their overall characterization of sites when cover estimation data were used, as assessed by cluster analysis, but methods agreed best on their overall characterization of sites when only presence/absence data were considered. Differences in abundance estimates as well as pseudoturnover contribute to variability. For double sampled plots, pseudoturnover was 19.1%, but 57.7% of pseudo-turnover cases involved taxa with , 0.5% cover while only 3.4% involved taxa with > 8% cover. We suggest that vegetation scientists incorporate quality control, calibrate observers and publish their results. [source] Optimal signal bandwidth for the recording of surface EMG activity of facial, jaw, oral, and neck musclesPSYCHOPHYSIOLOGY, Issue 1 2001A. van Boxtel Spontaneous pericranial electromyographic (EMG) activity is generally small and is contaminated by strong low-frequency artifacts. High-pass filtering should suppress artifacts but affect EMG signal power only minimally. In 24 subjects who performed a warned simple reaction time task, the optimal high-pass cut-off frequency was examined for nine different pericranial muscles. From four experimental conditions (visual and auditory reaction signals combined with hand and foot responses), 1-min EMG recordings were selected (bandwidth: 0.4,512 Hz) and divided into 60 1-s data segments. These segments were high-pass filtered, the ,3-dB cut-off frequency varying from 5 to 90 Hz, and subjected to power spectral analysis. Optimal high-pass filter frequencies were determined for the mean power spectra based on visual estimation or comparison with a theoretical spectrum of the artifact-free EMG signal. The optimal frequencies for the different muscles varied between 15 and 25 Hz and were not influenced by stimulus or response modality. For all muscles, a low-pass filter frequency between 400 and 500 Hz was appropriate. [source] | ||||||||||