Stability of Curvature Measures

We address the problem of curvature estimation from sampled compact sets. The main contribution is a stability result: we show that the gaussian, mean or anisotropic curvature measures of the offset of a compact set K with positive $\mu$-reach can be estimated by the same curvature measures of the offset of a compact set K' close to K in the Hausdorff sense. We show how these curvature measures can be computed for finite unions of balls. The curvature measures of the offset of a compact set with positive $\mu$-reach can thus be approximated by the curvature measures of the offset of a point-cloud sample. These results can also be interpreted as a framework for an effective and robust notion of curvature

Accretion of gas by globular cluster stars

Some recent observations of the abundances of s-process, r-process, and alpha elements in metal-poor stars have led to a new scenario for their formation. According to this scenario, these stars were born in a globular cluster and accreted the s-process enriched gas expelled by cluster stars of higher-mass, thereby modifying their surface abundances. Later on, these polluted stars evaporated from the globular cluster to constitute an important fraction of the current halo population. In addition, there are now many direct observations of abundance anomalies not only in globular cluster giant stars but also in subgiant and main-sequence stars. Accretion provides again a plausible explanation for (at least some of) these peculiarities. Here we investigate further the efficiency of the accretion scenario. We find that in concentrated clusters with large escape velocities, accretion is very efficient and can indeed lead to major modifications of the stellar surface abundances.Comment: 11 pages; accepted for publication in Astronomy and Astrophysic

Normal Cone Approximation and Offset Shape Isotopy

This work adresses the problem of the approximation of the normals of the offsets of general compact sets in euclidean spaces. It is proven that for general sampling conditions, it is possible to approximate the gradient vector field of the distance to general compact sets. These conditions involve the $\mu$-reach of the compact set, a recently introduced notion of feature size. As a consequence, we provide a sampling condition that is sufficient to ensure the correctness up to isotopy of a reconstruction given by an offset of the sampling. We also provide a notion of normal cone to general compact sets which is stable under perturbation

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Deep Metric Learning Based on Scalable Neighborhood Components for Remote Sensing Scene Characterization

With the development of convolutional neural networks (CNNs), the semantic understanding of remote sensing (RS) scenes has been significantly improved based on their prominent feature encoding capabilities. While many existing deep-learning models focus on designing different architectures, only a few works in the RS field have focused on investigating the performance of the learned feature embeddings and the associated metric space. In particular, two main loss functions have been exploited: the contrastive and the triplet loss. However, the straightforward application of these techniques to RS images may not be optimal in order to capture their neighborhood structures in the metric space due to the insufficient sampling of image pairs or triplets during the training stage and to the inherent semantic complexity of remotely sensed data. To solve these problems, we propose a new deep metric learning approach, which overcomes the limitation on the class discrimination by means of two different components: 1) scalable neighborhood component analysis (SNCA) that aims at discovering the neighborhood structure in the metric space and 2) the cross-entropy loss that aims at preserving the class discrimination capability based on the learned class prototypes. Moreover, in order to preserve feature consistency among all the minibatches during training, a novel optimization mechanism based on momentum update is introduced for minimizing the proposed loss. An extensive experimental comparison (using several state-of-the-art models and two different benchmark data sets) has been conducted to validate the effectiveness of the proposed method from different perspectives, including: 1) classification; 2) clustering; and 3) image retrieval. The related codes of this article will be made publicly available for reproducible research by the community

Acceptability of the interRAI Check-Up Self-Report Comprehensive Geriatric Assessment (CGA) Tool: Evaluating Check-Up Acceptability in Assessing Care Needs of Older Adults with Human Immunodeficiency Virus (HIV) in Kampala District of Uganda

Background: The Ugandan healthcare system is ill-equipped to manage the emerging medical and social needs of its aging population. With the high burden of human immunodeficiency virus (HIV), food insecurity, and the erosion of support systems, older adults are limited in their ability to maintain physical and emotional health and well-being. High levels of impairment in activities of daily living, cognition, and frailty associated with HIV coupled with increased multimorbidity for aging Ugandans calls for the revision of healthcare policies and evidence-informed practice. Objectives: This thesis aimed to estimate the association between HIV status and (i) activities of daily living, (ii) cognitive function, (iii) health stability, and (iv) clinical frailty in older persons living in Kampala, Uganda using the interRAI Check-Up self-report assessment instrument. Additionally, this thesis aimed to (v) evaluate assessment acceptability to inform healthcare system planning and care practices. Methods: A mixed methods design was employed. In Phase One, HIV-positive and negative older adults aged ≥60 years were assessed using the interRAI Check-Up self-report in the Nakawa division of Kampala. Patient characteristics were summarized with descriptive statistics, and a logistic regression analysis was used to identify differences in activities of daily living, cognitive function, health stability, and frailty of older persons in the study. In Phase Two, key informant interviews with service providers at the Reach Out Mbuya Community Health Initiative were held to characterize the acceptability of the Check-Up in the Ugandan setting and to explore perceptions of its use. Results: In Phase One, 130 Check-Up assessments were obtained for older persons in the community. HIV status was found to not be statistically significantly associated with the outcomes of interest and age was found to be positively associated with outcome scores for activities of daily living, cognitive performance, and frailty. However, age was not found to be associated with health stability. In Phase Two, 12 interviews were held with service providers at the Reach Out Mbuya Community Health Initiative. The Check-Up was found to be acceptable for use in the Ugandan setting, with minor gaps identified for coverage of economic stability, food security, living arrangement, and the physical environment. Further, challenges with languages offered, the technology required, and length of time to complete was discussed. Discussion: Findings of age-related associations for activities of daily living, cognitive performance, and frailty were conclusive with expectations for the trajectory of health throughout the aging process. Similarities across HIV-positive and negative participants are attributed to participant age, low study sample size, viral suppression, and healthcare service utilization. For Check-Up use in the Ugandan setting, several recommendations are made to address identified gaps including question modifications, further translations, provision of additional tablets, and granted permissions to RAIsoft. Next, capacity training for Check-Up use by service providers is introduced, including the need for sensitization of gender differences and appropriate structuring of assessors in the field. Lastly, a theoretical framework assessment revealed barriers in the ability of the Theoretical Framework of Acceptability to identify key gender and socio-cultural differences in intervention recipients and deliverers. Implications: This thesis provided important information for describing the needs of aging Ugandans and insight into how a standardized instrument can help to support the development of a geriatric-friendly healthcare system across the nation. This was an important step in establishing an interRAI community of practice in East Africa

The influence of earth surface movements and human activities on the river Karun in lowland south-west Iran

Earth surface movements are a primary external control on river system dynamics and evolution. It has often been observed that when responding to Earth surface motion driven by surface expression of folds, major rivers incise across young, active folds near their structural culminations and divert around others. This study shows that for the major rivers Karun and Dez in the Mesopotamian-Persian Gulf foreland basin, these different river responses are due to the need for narrow channel-belts to be maintained where a river incises across a fold, and the time it takes (at least several decades) for such narrow channel-belts to develop. In general, where a major river initially encounters a fold as an emerging fold “core”, the river flows across the uplifting fold for sufficient time for the development of a narrow channel-belt, thus producing an incising river course across the fold (a single “water gap”) in the vicinity of the fold “core” and the subsequent structural culmination. However, where a major river initially encounters a fold as a larger, emerged fold, the river does not flow across the uplifting fold for sufficient time, due to channel migration in response to lateral fold growth, thus producing a river course diverting around the fold “nose”. Hence, river reaches across the fold axis for river incision are characterised by narrow channel-belts, low channel sinuosities, high specific stream powers, and river crossing locations relatively near to the fold “core” (generally nearer than 16 km). By contrast, river reaches across the fold axis projection for river diversion are characterised by average channel-belt widths and channel sinuosities with fairly wide ranging values, fairly low specific stream powers, and river crossing locations relatively far from the fold “core” (further than 22 km). A narrow average channel-belt width of less than c. 2.7 km is a threshold for the rivers Karun and Dez (mean annual discharges c. 575 m³s¯¹ and 230 m³s¯¹) encountering folds in lowland south-west Iran (rates of uplift c. 0.1 - 2.3 mm yr¯¹), and this probably has a precedence over other geomorphological changes for producing river incision across a fold in response to uplift. In general, slightly smaller rivers are more frequently diverted around the fold “nose”, and small rivers and creeks, which are more easily “defeated” by fold growth, frequently develop a series of narrow “wind gaps” across a fold.The influences of human impacts on major rivers can be distinguished from those of Earth surface movements by suites of river characteristics. There may be significant interactions where these two external factors coincide, most notably where fold uplift and major anthropogenic river channel straightening produce the persistence of long, near-straight river courses (channel sinuosity 10 km long)