Deep Unsupervised Similarity Learning using Partially Ordered Sets

Unsupervised learning of visual similarities is of paramount importance to computer vision, particularly due to lacking training data for fine-grained similarities. Deep learning of similarities is often based on relationships between pairs or triplets of samples. Many of these relations are unreliable and mutually contradicting, implying inconsistencies when trained without supervision information that relates different tuples or triplets to each other. To overcome this problem, we use local estimates of reliable (dis-)similarities to initially group samples into compact surrogate classes and use local partial orders of samples to classes to link classes to each other. Similarity learning is then formulated as a partial ordering task with soft correspondences of all samples to classes. Adopting a strategy of self-supervision, a CNN is trained to optimally represent samples in a mutually consistent manner while updating the classes. The similarity learning and grouping procedure are integrated in a single model and optimized jointly. The proposed unsupervised approach shows competitive performance on detailed pose estimation and object classification.Comment: Accepted for publication at IEEE Computer Vision and Pattern Recognition 201

Beyond One-hot Encoding: lower dimensional target embedding

Target encoding plays a central role when learning Convolutional Neural Networks. In this realm, One-hot encoding is the most prevalent strategy due to its simplicity. However, this so widespread encoding schema assumes a flat label space, thus ignoring rich relationships existing among labels that can be exploited during training. In large-scale datasets, data does not span the full label space, but instead lies in a low-dimensional output manifold. Following this observation, we embed the targets into a low-dimensional space, drastically improving convergence speed while preserving accuracy. Our contribution is two fold: (i) We show that random projections of the label space are a valid tool to find such lower dimensional embeddings, boosting dramatically convergence rates at zero computational cost; and (ii) we propose a normalized eigenrepresentation of the class manifold that encodes the targets with minimal information loss, improving the accuracy of random projections encoding while enjoying the same convergence rates. Experiments on CIFAR-100, CUB200-2011, Imagenet, and MIT Places demonstrate that the proposed approach drastically improves convergence speed while reaching very competitive accuracy rates.Comment: Published at Image and Vision Computin

Using Hidden Markov Models for Land Surface Phenology: An Evaluation Across a Range of Land Cover Types in Southeast Spain

Land Surface Phenology (LSP) metrics are increasingly being used as indicators of climate change impacts in ecosystems. For this purpose, it is necessary to use methods that can be applied to large areas with different types of vegetation, including vulnerable semiarid ecosystems that exhibit high spatial variability and low signal-to-noise ratio in seasonality. In this work, we evaluated the use of hidden Markov models (HMM) to extract phenological parameters from Moderate Resolution Imaging Spectroradiometer (MODIS) derived Normalized Difference Vegetation Index (NDVI). We analyzed NDVI time-series data for the period 2000–2018 across a range of land cover types in Southeast Spain, including rice croplands, shrublands, mixed pine forests, and semiarid steppes. Start of Season (SOS) and End of Season (EOS) metrics derived from HMM were compared with those obtained using well-established smoothing methods. When a clear and consistent seasonal variation was present, as was the case in the rice croplands, and when adjusting average curves, the smoothing methods performed as well as expected, with HMM providing consistent results. When spatial variability was high and seasonality was less clearly defined, as in the semiarid shrublands and steppe, the performance of the smoothing methods degraded. In these cases, the results from HMM were also less consistent, yet they were able to provide pixel-wise estimations of the metrics even when comparison methods did not.This research was funded by Ministerio de Economía y Competitividad grant numbers CGL2017-89804-R, CGL2014-59074-R, and CGL2015-69773-C2-1-P

Comparing surgically induced astigmatism calculated by means of simulated keratometry versus total corneal refractive power

Purpose: To evaluate surgically induced astigmatism as computed by means of either simulated keratometry (KSIM) or total corneal refractive power (TCRP) after temporal incisions. Methods: Prospective observational study including 36 right eyes undergoing cataract surgery. Astigmatism was measured preoperatively during the 3-month follow-up period using Pentacam. Surgically induced astigmatism was computed considering anterior corneal surface astigmatism at 3mm with KSIM and considering both corneal surfaces with TCRP from 1 to 8mm (TCRP3 for 3mm). The eyes under study were divided into two balanced groups: LOW with KSIM astigmatism <0.90D and HIGH with KSIM astigmatism ≥0.90D. Resulting surgically induced astigmatism values were compared across groups and measuring techniques by means of flattening, steepening, and torque analysis. Results: Mean surgically induced astigmatism was higher in the HIGH group (0.31D @ 102°) than in the LOW group (0.04 D @ 16°). The temporal incision resulted in a steepening in the HIGH group of 0.15 D @ 90°, as estimated with KSIM, versus 0.28 D @ 90° with TCRP3, but no significant differences were found for the steepening in the LOW group or for the torque in either group. Differences between KSIM- and TCRP3-based surgically induced astigmatism values were negligible in LOW group. Conclusion: Surgically induced astigmatism was considerably higher in the high-astigmatism group and its value was underestimated with the KSIM approach. Eyes having low astigmatism should not be included for computing the surgically induced astigmatism because steepening would be underestimated

Gait speed as a mediator of the effect of sarcopenia on dependency in activities of daily living

Background Sarcopenia in older adults is strongly associated with an increase in dependency in activities of daily living (ADL) and with a decline in gait speed. Interestingly, gait speed has been shown to independently predict mortality. In this context, our study aimed to explore the mediator role of gait speed on the relationship between sarcopenia and dependency in ADL. Methods A cross-sectional study was conducted in Colombia, 19 705 older adults with a mean age of 70 years, 55.6% women, 16.1% with sarcopenia, and 14.7% mild, moderate, or severe dependency in ADL, according to ‘SABE Survey 2015’. Sarcopenia was assessed by calf circumference and ADL dependence through the Barthel Index. Gait speed was measured over a distance of 3 m. The association between sarcopenia condition and gait speed and dependency level was analysed by linear regression adjusted by covariates. To examine whether gait speed mediated the association between sarcopenia and dependence components of physical function, simple mediation models were generated using ordinary least squares with the macro PROCESS version 3.2, adjusted for age, sex, and body mass index (BMI). Results Significant differences (P < 0.05) were found in gait speed and dependency in ADL between the sarcopenia and nonsarcopenia groups after adjusting for age, sex, and BMI. BMI was significantly higher in the non-sarcopenia group whereas dependency was significantly higher in the sarcopenia group (19.6% vs. 13.8%). Results from mediation model regression analysis indicated a significant and direct detrimental effect of sarcopenia on dependency in ADL (β = 0.05; P < 0.001), and a significant indirect effect of gait speed on the direct effect ( 0.009 to 0.004). Conclusions The negative effect of sarcopenia on functional dependence was mediated by the gait speed. Therefore, gait speed may positively influence the detrimental effect of sarcopenia for dependency, after adjusting for age, gender, and BMI. Consequently, physical exercise should be promoted and focused to circumvent the gait speed decline associated with age in older people with sarcopenia

Comparative and functional genomics of the protozoan parasite Babesia divergens highlighting the invasion and egress processes

Babesiosis is considered an emerging disease because its incidence has significantly increased in the last 30 years, providing evidence of the expanding range of this rare but potentially life-threatening zoonotic disease. Babesia divergens is a causative agent of babesiosis in humans and cattle in Europe. The recently sequenced genome of B. divergens revealed over 3,741 protein coding-genes and the 10.7-Mb high-quality draft become the first reference tool to study the genome structure of B. divergens. Now, by exploiting this sequence data and using new computational tools and assembly strategies, we have significantly improved the quality of the B. divergens genome. The new assembly shows better continuity and has a higher correspondence to B. bovis chromosomes. Moreover, we present a differential expression analysis using RNA sequencing of the two different stages of the asexual lifecycle of B. divergens: the free merozoite capable of invading erythrocytes and the intraerythrocytic parasite stage that remains within the erythrocyte until egress. Comparison of mRNA levels of both stages identified 1,441 differentially expressed genes. From these, around half were upregulated and the other half downregulated in the intraerythrocytic stage. Orthogonal validation by real-time quantitative reverse transcription PCR confirmed the differential expression. A moderately increased expression level of genes, putatively involved in the invasion and egress processes, were revealed in the intraerythrocytic stage compared with the free merozoite. On the basis of these results and in the absence of molecular models of invasion and egress for B. divergens, we have proposed the identified genes as putative molecular players in the invasion and egress processes. Our results contribute to an understanding of key parasitic strategies and pathogenesis and could be a valuable genomic resource to exploit for the design of diagnostic methods, drugs and vaccines to improve the control of babesiosis.This work was funded by grants from Ministerio de Economía y Competitividad from Spain (AGL2010-21774 and AGL2014-56193 R to EM and LMG). ES was awarded a research fellowship from Plan Estatal de Investigación Científica y Técnica y de Innovación, Ministerio de Economía y Competitividad, Spain (http://www.mineco.gob.es/portal/site/mineco/). Work in CL’s laboratory is funded by a grant from the National Institutes of Health (https://www.nih.gov/) NIH- 1R01HL140625-01. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscriptS

Microvascular cutaneous coverage in wounds that expose the Achilles tendon: case report

Achilles tendon rupture, being one of the main tendon ruptures present, surgery being the most favourable option even taking into account complications such as infections and skin necrosis, it is necessary to develop techniques which help to reduce complications and increase benefits. The methods follow-up of 2 cases of patients with skin defects in the region of the Achilles tendon in patients who were treated at the "Luis Guillermo lbarra lbarra" national rehabilitation institute during the period 2020-2021 in the Traumatology service, treated with radial free flap forearm, using the description of the most used flaps in the literature. Results in both cases integrity of the free radial forearm flap in its entirety, functional recovery for walking, ability to put shoes back on, and without the need for reoperation, as well as a high level of satisfaction by patients. Conclusions if we are talking about an Achilles tendon rupture with a significant skin defect, the free radial forearm flap is an adequate option, if we are talking about a complete defect, the composite flap is the best option, remember that the decision on what type of flap will be used will depend on of the size of the lesion