This study aimed to assess the perceived efficacy of aligners (Invisalign; Align Technology, Santa Clara, Calif) at performing extrusive movements of maxillary lateral incisors and to evaluate and ...compare differences in treatment planning protocols and other interventions used when required between orthodontists and general dentists with various degrees of experience.
An original 18-question survey was sent by mail to a randomized and geographically proportionate selection of orthodontic specialists (N = 400) and general dentists (N = 400) listed as providers on the Invisalign Web site. The data were analyzed using analysis of variance and chi-square tests.
One hundred twenty-six providers responded to the survey (15.8% response rate), including 36 general dentists and 90 orthodontists. Overall, the average perceived efficacy was 4.71 out of 10 (95% confidence interval, 4.28-5.14). The threshold for identification of tracking issues was significantly associated with provider type (P = 0.0305). General dentists were significantly more likely to prefer an optimized attachment (P = 0.0001), whereas orthodontists were significantly more likely to prefer a gingivally-beveled horizontal rectangular attachment (P <0.0001). A refinement scan was the most common intervention method, followed by the bootstrap technique.
The average perceived efficacy for extruding maxillary lateral incisors with aligners was 4.71 out of 10. Orthodontists had a lower tolerance than general dentists for tracking issues. A refinement scan was the most common method of intervention. General dentists and orthodontists differed in their treatment planning preferences and timing of intervention.
•Aligners are perceived as only moderately effective at extruding maxillary lateral incisors.•Orthodontists mostly preferred a gingivally-beveled horizontal rectangular attachment.•Orthodontists are more critical of tracking issues than general dentists.•A refinement scan was the most common method of intervention for tracking issues.•Orthodontists wait until the end of the series to take a refinement scan.
To evaluate the color stability and mechanical properties of two commonly used maxillofacial silicone elastomers after addition of pigments and opacifiers and before and after artificial aging.
This ...study evaluated two maxillofacial silicone elastomers: A-2000 and M511. Two different pigment and opacifier systems (e-Skin and Reality Series) were used with the elastomers. Control groups (no pigment or opacifier) and experimental groups (each with subgroups containing additional pigments and/ or opacifiers) were fabricated for each of the silicone elastomers. A total of 51 specimens were evaluated for color stability, and 100 for mechanical properties. A spectrophotometer was used to assess CIE L*a*b* values before and after aging. CIELAB 50:50% perceptibility threshold (ΔE* = 1.1) and acceptability threshold (ΔE* = 3.0) were used to interpret color changes. A durometer and universal testing machine were used to evaluate the mechanical properties. ANOVA and Fisher least significant difference (LSD) test were performed to determine the statistical significance of the results (P < .05).
Significant differences in color measurements (ΔE*) were found for all silicone groups following artificial aging (P < .05). ΔE* values for the mixed pigment/opacifier subgroups of both elastomers were below the perceptibility threshold. Additionally, after aging, the hardness, tear strength, and tensile strength significantly increased for all silicone groups (P < .05), while percent elongation significantly decreased (P < .05).
Artificial aging affected the color stability and mechanical properties of the pigmented silicone elastomers with added opacifier. Overall, A-2000 with e-Skin group displayed the most color stability, with its mechanical properties being the least affected by artificial aging.
Very high resolution synthetic aperture radar (SAR) sensors represent an alternative to aerial photography for delineating floods in built-up environments where flood risk is highest. However, even ...with currently available SAR image resolutions of 3 m and higher, signal returns from man-made structures hamper the accurate mapping of flooded areas. Enhanced image processing algorithms and a better exploitation of image archives are required to facilitate the use of microwave remote-sensing data for monitoring flood dynamics in urban areas. In this paper, a hybrid methodology combining backscatter thresholding, region growing, and change detection (CD) is introduced as an approach enabling the automated, objective, and reliable flood extent extraction from very high resolution urban SAR images. The method is based on the calibration of a statistical distribution of "open water" backscatter values from images of floods. Images acquired during dry conditions enable the identification of areas that are not "visible" to the sensor (i.e., regions affected by "shadow") and that systematically behave as specular reflectors (e.g., smooth tarmac, permanent water bodies). CD with respect to a reference image thereby reduces overdetection of inundated areas. A case study of the July 2007 Severn River flood (UK) observed by airborne photography and the very high resolution SAR sensor on board TerraSAR-X highlights advantages and limitations of the method. Even though the proposed fully automated SAR-based flood-mapping technique overcomes some limitations of previous methods, further technological and methodological improvements are necessary for SAR-based flood detection in urban areas to match the mapping capability of high-quality aerial photography.
Flood Detection in Urban Areas Using TerraSAR-X Mason, D.C.; Speck, R.; Devereux, B. ...
IEEE transactions on geoscience and remote sensing,
2010-Feb., 2010-02-00, 20100201, Letnik:
48, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Flooding is a major hazard in both rural and urban areas worldwide, but it is in urban areas that the impacts are most severe. An investigation of the ability of high-resolution TerraSAR-X synthetic ...aperture radar (SAR) data to detect flooded regions in urban areas is described. The study uses a TerraSAR-X image of a one-in-150-year flood near Tewkesbury, U.K., in 2007, for which contemporaneous aerial photography exists for validation. The German Aerospace Center (DLR) SAR end-to-end simulator (SETES) was used in conjunction with airborne scanning laser altimetry (LiDAR) data to estimate regions of the image in which water would not be visible due to shadow or layover caused by buildings and taller vegetation. A semiautomatic algorithm for the detection of floodwater in urban areas is described, together with its validation using aerial photographs. Of the urban water pixels that are visible to TerraSAR-X, 76% were correctly detected, with an associated false positive rate of 25%. If all the urban water pixels were considered, including those in shadow and layover regions, these figures fell to 58% and 19%, respectively. The algorithm is aimed at producing urban flood extents with which to calibrate and validate urban flood inundation models, and these findings indicate that TerraSAR-X is capable of providing useful data for this purpose.
A near real-time flood detection algorithm giving a synoptic overview of the extent of flooding in both urban and rural areas, and capable of working during night-time and day-time even if cloud was ...present, could be a useful tool for operational flood relief management. The paper describes an automatic algorithm using high-resolution synthetic aperture radar (SAR) satellite data that builds on existing approaches, including the use of image segmentation techniques prior to object classification to cope with the very large number of pixels in these scenes. Flood detection in urban areas is guided by the flood extent derived in adjacent rural areas. The algorithm assumes that high-resolution topographic height data are available for at least the urban areas of the scene, in order that a SAR simulator may be used to estimate areas of radar shadow and layover. The algorithm proved capable of detecting flooding in rural areas using TerraSAR-X with good accuracy, classifying 89% of flooded pixels correctly, with an associated false positive rate of 6%. Of the urban water pixels visible to TerraSAR-X, 75% were correctly detected, with a false positive rate of 24%. If all urban water pixels were considered, including those in shadow and layover regions, these figures fell to 57% and 18%, respectively.
A traditional method of validating the performance of a flood model when remotely sensed data of the flood extent are available is to compare the predicted flood extent to that observed. The ...performance measure employed often uses areal pattern-matching to assess the degree to which the two extents overlap. Recently, remote sensing of flood extents using synthetic aperture radar (SAR) and airborne scanning laser altimetry (LiDAR) has made more straightforward the synoptic measurement of water surface elevations along flood boundaries (waterlines), and this has emphasised the possibility of using alternative performance measures based on height. This paper considers the advantages that can accrue from using a performance measure based on waterline elevations rather than one based on areal patterns of wet and dry pixels. The two measures were compared for their ability to estimate flood inundation uncertainty maps from a set of LISFLOOD-FP model runs carried out to span the acceptable model parameter range. A 1-in-5-year flood on the Thames in 1992, observed in an ERS-1 SAR image, was used as a test event. Waterlines were delineated in fused SAR and LiDAR data using an active contour model (snake). The performance measure based on height differences of corresponding points along the observed and modelled waterlines was found to be significantly more sensitive to the channel friction parameter than the measure based on areal patterns of flood extent. A result of this was that there was less uncertainty in the final flood hazard map. The height-based measure was found to be more sensitive when increased heighting accuracy was achieved by requiring that observed waterline heights varied slowly along the reach. The technique was shown to allow the decomposition of the reach into sections, with different effective channel friction parameters used in different sections. However, an evaluation of the modelled inundation uncertainty using the calibration event showed significant differences between the uncertainty map and the observed flood extent, especially for the height-based measure. This was probably due to the conceptually simple flood inundation model and the coarse application resolution employed in this case. The increased sensitivity of the height-based measure may lead to an increased onus being placed on the model developer in the production of a valid model.
In 2010, a tissue‐engineered trachea was transplanted into a 10‐year‐old child using a decellularized deceased donor trachea repopulated with the recipient's respiratory epithelium and mesenchymal ...stromal cells. We report the child's clinical progress, tracheal epithelialization and costs over the 4 years. A chronology of events was derived from clinical notes and costs determined using reference costs per procedure. Serial tracheoscopy images, lung function tests and anti‐HLA blood samples were compared. Epithelial morphology and T cell, Ki67 and cleaved caspase 3 activity were examined. Computational fluid dynamic simulations determined flow, velocity and airway pressure drops. After the first year following transplantation, the number of interventions fell and the child is currently clinically well and continues in education. Endoscopy demonstrated a complete mucosal lining at 15 months, despite retention of a stent. Histocytology indicates a differentiated respiratory layer and no abnormal immune activity. Computational fluid dynamic analysis demonstrated increased velocity and pressure drops around a distal tracheal narrowing. Cross‐sectional area analysis showed restriction of growth within an area of in‐stent stenosis. This report demonstrates the long‐term viability of a decellularized tissue‐engineered trachea within a child. Further research is needed to develop bioengineered pediatric tracheal replacements with lower morbidity, better biomechanics and lower costs.
This case presents a 4‐year follow‐up of a tissue‐engineered pediatric tracheal transplant and reports on the longterm viability of this approach and areas for further research.
► Uncertainty in observed data can influence the assessment of model performance. ► The assessment of model performance using spatial pattern comparisons should be avoided where possible. ► A ...probabilistic treatment of observed data should be used to gain a more holistic understanding of flood risk.
The performance of flood inundation models is often assessed using satellite observed data; however, these data have inherent uncertainty. In this study we determine the patterns of uncertainty in an ERS-2 SAR image of flooding on the River Dee, UK and, using LISFLOOD-FP, evaluate how this uncertainty can influence the assessment of flood inundation model performance. The flood outline is intersected with high resolution LiDAR topographic data to extract water levels at the flood margin, and to estimate patterns of uncertainty the gauged water levels are used to create a reference water surface slope for comparison with the satellite-derived water levels. We find the residuals between the satellite data points and the reference line to be spatially clustered.
A new method of evaluating model performance is developed to test the impact of this spatial dependency on model calibration. This method uses multiple random subsamples of the water surface elevation points that have no significant spatial dependency; tested for using Moran’s I. LISFLOOD-FP is then calibrated using conventional binary pattern matching and water elevation comparison both with and without spatial dependency. It is shown that model calibration carried out using pattern matching is negatively influenced by spatial dependency in the data. By contrast, calibration using water elevations produces realistic calibrated optimum friction parameters even when spatial dependency is present. Accounting for spatial dependency reduces the estimated modelled error and gives an identical result to calibration using spatially dependent data; it also has the advantage of being a statistically robust assessment of model performance in which we can have more confidence. Further, by using the variations found in the subsamples of the observed data it is possible to assess how the noisiness in these data affects our understanding of flood risk. This has highlighted the requirement for a probabilistic treatment of observed data, and using multiple subsamples is one way of achieving this.
Why are some individuals more likely to become owners of small businesses than others? We classify industries using measures of entry barriers and proceed to investigate how determinants of entry ...vary in high- as opposed to low-barrier fields. Claims that neither financial-capital constraints nor the educational backgrounds of aspiring small-business owners predict the likelihood of small-business entry are investigated in this context. These claims of irrelevance, we find, are inconsistent with the facts. The wealth and educational background characteristics potential entrepreneurs possess predispose them to make distinctly different industry choices, both because of the differing rewards available to them and the very different entry barriers they face. The characteristics of potential entrants, in other words, draw them toward some industries and away from others.
► Traits of potential entrepreneurs draw them toward some types of new ventures and away from others. ► High personal wealth sometimes predicts entrepreneurial entry and sometimes it doesn't. ► The college graduate trait negatively predicts entry into many lines of small business.
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