Dimension Distortion by Sobolev Mappings in Foliated Metric Spaces

We quantify the extent to which a supercritical Sobolev mapping can increase the dimension of subsets of its domain, in the setting of metric measure spaces supporting a Poincaré inequality. We show that the set of mappings that distort the dimensions of sets by the maximum possible amount is a prevalent subset of the relevant function space. For foliations of a metric space X defined by a David–Semmes regular mapping Π : X → W, we quantitatively estimate, in terms of Hausdorff dimension in W, the size of the set of leaves of the foliation that are mapped onto sets of higher dimension. We discuss key examples of such foliations, including foliations of the Heisenberg group by left and right cosets of horizontal subgroups.

Frequency of Sobolev and quasiconformal dimension distortion

We study Hausdorff and Minkowski dimension distortion for images of generic affine subspaces of Euclidean space under Sobolev and quasiconformal maps. For a supercritical Sobolev map f defined on a domain in RnRn, we estimate from above the Hausdorff dimension of the set of affine subspaces parallel to a fixed m-dimensional linear subspace, whose image under f has positive HαHα measure for some fixed α>mα>m. As a consequence, we obtain new dimension distortion and absolute continuity statements valid for almost every affine subspace. Our results hold for mappings taking values in arbitrary metric spaces, yet are new even for quasiconformal maps of the plane. We illustrate our results with numerous examples.

A new method to measure higher visual functions in an immersive environment

BACKGROUND: Higher visual functions can be defined as cognitive processes responsible for object recognition, color and shape perception, and motion detection. People with impaired higher visual functions after unilateral brain lesion are often tested with paper pencil tests, but such tests do not assess the degree of interaction between the healthy brain hemisphere and the impaired one. Hence, visual functions are not tested separately in the contralesional and ipsilesional visual hemifields. METHODS: A new measurement setup, that involves real-time comparisons of shape and size of objects, orientation of lines, speed and direction of moving patterns, in the right or left visual hemifield, has been developed. The setup was implemented in an immersive environment like a hemisphere to take into account the effects of peripheral and central vision, and eventual visual field losses. Due to the non-flat screen of the hemisphere, a distortion algorithm was needed to adapt the projected images to the surface. Several approaches were studied and, based on a comparison between projected images and original ones, the best one was used for the implementation of the test. Fifty-seven healthy volunteers were then tested in a pilot study. A Satisfaction Questionnaire was used to assess the usability of the new measurement setup. RESULTS: The results of the distortion algorithm showed a structural similarity between the warped images and the original ones higher than 97%. The results of the pilot study showed an accuracy in comparing images in the two visual hemifields of 0.18 visual degrees and 0.19 visual degrees for size and shape discrimination, respectively, 2.56° for line orientation, 0.33 visual degrees/s for speed perception and 7.41° for recognition of motion direction. The outcome of the Satisfaction Questionnaire showed a high acceptance of the battery by the participants. CONCLUSIONS: A new method to measure higher visual functions in an immersive environment was presented. The study focused on the usability of the developed battery rather than the performance at the visual tasks. A battery of five subtasks to study the perception of size, shape, orientation, speed and motion direction was developed. The test setup is now ready to be tested in neurological patients.

Elicitable distortion risk measures: A concise proof

Elicitability has recently been discussed as a desirable property for risk measures. Kou and Peng (2014) showed that an elicitable distortion risk measure is either a Value-at-Risk or the mean. We give a concise alternative proof of this result, and discuss the conflict between comonotonic additivity and elicitability.

An examination chair to measure internal rotation of the hip in routine settings: a validation study

OBJECTIVE: To determine the performance of a newly developed examination chair as compared with the clinical standard of assessing internal rotation (IR) of the flexed hip with a goniometer. METHODS: The examination chair allowed measurement of IR in a sitting position simultaneously in both hips, with hips and knees flexed 90 degrees, lower legs hanging unsupported and a standardized load of 5 kg applied to both ankles using a bilateral pulley system. Clinical assessment of IR was performed in supine position with hips and knees flexed 90 degrees using a goniometer. Within the framework of a population-based inception cohort study, we calculated inter-observer agreement in two samples of 84 and 64 consecutive, unselected young asymptomatic males using intra-class correlation coefficients (ICC) and determined the correlation between IR assessed with examination chair and clinical assessment. RESULTS: Inter-observer agreement was excellent for the examination chair (ICC right hip, 0.92, 95% confidence interval [CI] 0.89-0.95; ICC left hip, 0.90, 95% CI 0.86-0.94), and considerably higher than that seen with clinical assessment (ICC right hip, 0.65, 95% CI 0.49-0.77; ICC left hip, 0.69, 95% CI 0.54-0.80, P for difference in ICC between examination chair and clinical assessment

A method to measure the distribution of latencies of motor evoked potentials in man

To measure the intra-individual distribution of the latencies of motor evoked potentials (MepL) using transcranial magnetic stimulation.

Validity of an automatic measure protocol in distal femur for allograft selection from a three-dimensional virtual bone bank system

Osteoarticular allograft is one possible treatment in wide surgical resections with large defects. Performing best osteoarticular allograft selection is of great relevance for optimal exploitation of the bone databank, good surgery outcome and patient’s recovery. Current approaches are, however, very time consuming hindering these points in practice. We present a validation study of a software able to perform automatic bone measurements used to automatically assess the distal femur sizes across a databank. 170 distal femur surfaces were reconstructed from CT data and measured manually using a size measure protocol taking into account the transepicondyler distance (A), anterior-posterior distance in medial condyle (B) and anterior-posterior distance in lateral condyle (C). Intra- and inter-observer studies were conducted and regarded as ground truth measurements. Manual and automatic measures were compared. For the automatic measurements, the correlation coefficients between observer one and automatic method, were of 0.99 for A measure and 0.96 for B and C measures. The average time needed to perform the measurements was of 16 h for both manual measurements, and of 3 min for the automatic method. Results demonstrate the high reliability and, most importantly, high repeatability of the proposed approach, and considerable speed-up on the planning.

Quantitative multiparameter assays to measure the effect of adjuvants on human antigen-specific CD8 T-cell responses

Large numbers and functionally competent T cells are required to protect from diseases for which antibody-based vaccines have consistently failed (1), which is the case for many chronic viral infections and solid tumors. Therefore, therapeutic vaccines aim at the induction of strong antigen-specific T-cell responses. Novel adjuvants have considerably improved the capacity of synthetic vaccines to activate T cells, but more research is necessary to identify optimal compositions of potent vaccine formulations. Consequently, there is a great need to develop accurate methods for the efficient identification of antigen-specific T cells and the assessment of their functional characteristics directly ex vivo. In this regard, hundreds of clinical vaccination trials have been implemented during the last 15 years, and monitoring techniques become more and more standardized.

Reliability, construct and criterion validity of the KIDSCREEN-10 score: a short measure for children and adolescents' well-being and health-related quality of life

Background To assess the criterion and construct validity of the KIDSCREEN-10 well-being and health-related quality of life (HRQoL) score, a short version of the KIDSCREEN-52 and KIDSCREEN-27 instruments. Methods The child self-report and parent report versions of the KIDSCREEN-10 were tested in a sample of 22,830 European children and adolescents aged 8–18 and their parents (n = 16,237). Correlation with the KIDSCREEN-52 and associations with other generic HRQoL measures, physical and mental health, and socioeconomic status were examined. Score differences by age, gender, and country were investigated. Results Correlations between the 10-item KIDSCREEN score and KIDSCREEN-52 scales ranged from r = 0.24 to 0.72 (r = 0.27–0.72) for the self-report version (proxy-report version). Coefficients below r = 0.5 were observed for the KIDSCREEN-52 dimensions Financial Resources and Being Bullied only. Cronbach alpha was 0.82 (0.78), test–retest reliability was ICC = 0.70 (0.67) for the self- (proxy-)report version. Correlations between other children self-completed HRQoL questionnaires and KIDSCREEN-10 ranged from r = 0.43 to r = 0.63 for the KIDSCREEN children self-report and r = 0.22–0.40 for the KIDSCREEN parent proxy report. Known group differences in HRQoL between physically/mentally healthy and ill children were observed in the KIDSCREEN-10 self and proxy scores. Associations with self-reported psychosomatic complaints were r = −0.52 (−0.36) for the KIDSCREEN-10 self-report (proxy-report). Statistically significant differences in KIDSCREEN-10 self and proxy scores were found by socioeconomic status, age, and gender. Conclusions Our results indicate that the KIDSCREEN-10 provides a valid measure of a general HRQoL factor in children and adolescents, but the instrument does not represent well most of the single dimensions of the original KIDSCREEN-52. Test–retest reliability was slightly below a priori defined thresholds.