Self-Supervised Learning with an Information Maximization Criterion

Self-supervised learning allows AI systems to learn effective representations from large amounts of data using tasks that do not require costly labeling. Mode collapse, i.e., the model producing identical representations for all inputs, is a central problem to many self-supervised learning approaches, making self-supervised tasks, such as matching distorted variants of the inputs, ineffective. In this article, we argue that a straightforward application of information maximization among alternative latent representations of the same input naturally solves the collapse problem and achieves competitive empirical results. We propose a self-supervised learning method, CorInfoMax, that uses a second-order statistics-based mutual information measure that reflects the level of correlation among its arguments. Maximizing this correlative information measure between alternative representations of the same input serves two purposes: (1) it avoids the collapse problem by generating feature vectors with non-degenerate covariances; (2) it establishes relevance among alternative representations by increasing the linear dependence among them. An approximation of the proposed information maximization objective simplifies to a Euclidean distance-based objective function regularized by the log-determinant of the feature covariance matrix. The regularization term acts as a natural barrier against feature space degeneracy. Consequently, beyond avoiding complete output collapse to a single point, the proposed approach also prevents dimensional collapse by encouraging the spread of information across the whole feature space. Numerical experiments demonstrate that CorInfoMax achieves better or competitive performance results relative to the state-of-the-art SSL approaches

Combined transdiaphragmatic off-pump and minimally invasive coronary artery bypass with right gastroepiploic artery and abdominal aortic aneurysm repair

Objective: Rare diseas

Does pulmonary artery venting decrease the incidence of postoperative atrial fibrillation after conventional aortocoronary bypass surgery?

Objectives: In this study, we tested the hypothesis that pulmonary artery venting would decrease the incidence of atrial fibrillation after coronary artery bypass surgery. Methods: This prospective study included 301 patients who underwent complete myocardial revascularization with cardiopulmonary bypass in our department during a 2-year period. The patients were randomly divided into 2 groups: group I included 151 patients who underwent aortic root venting and group II included 150 patients who underwent pulmonary arterial venting for decompression of the left heart. Pre-, peri-, and postoperative risk factors for atrial fibrillation were assessed in both groups. Results: The mean age was similar in the 2 groups. The mean number of anastomoses was significantly higher in group I (2.8 ± 0.8) than in group II (2.4 ± 0.8) (P = 0.001). The mean cross-clamp time was 42.7 ± 17.4 minutes in group I and 54.1 ± 23.8 minutes in group II (P = 0.001). The mean cardiopulmonary bypass time was 66.4 ± 46.1 minutes in group I and 77.4 ± 28.6 minutes in group II (P = 0.08). The incidence of atrial fibrillation was 14.5% (n = 21) in group I and 6.5% (n = 10) in group II (P = 0.02). Multivariate regression analysis showed that pulmonary artery venting decreased the postoperative incidence of atrial fibrillation by 17.6%. Conclusions: Pulmonary arterial venting may be used as an alternative to aortic root venting during on-pump coronary bypass surgery, especially in patients at high risk of postoperative atrial fibrillation. © 2013 Forum Multimedia Publishing, LLC

Coronary artery bypass graft surgery in a patient with ureterosigmoidostomy

A 75-year-old male patient had stable angina pectoris. After coronary angiography we decided to perform a coronary artery bypass graft surgery. Twenty years ago the patient underwent radical cystectomy and bilateral ureterosigmoidostomy because of bladder cancer. After that, his micturition was via the rectum. We did not experience that before. As is known, monitoring of urine output is very important after cardiac surgery. The patient was consulted with an urologist for how to monitor urine output in him. Transrectal catheterization was recommended for our follow-up, but before the catheterization bowel cleansing is necessary. Four-vessel on-pump coronary artery bypass graft surgery was performed without any problem. Peroperative urine volume and arterial blood gas results were normal. Urine output is a sensitive variable reflecting the patient's effective blood volume and tissue perfusion. Urinary catheterization is a standard for all cardiac surgeries, and it allows the patients' urine to drain freely from the bladder for collection. Monitoring of urine output in patients with ureterosigmoidostomy is impossible by standard urinary catheterization method. In this case we performed transrectal catheterization for Urine flow follow-up. Urine flow follow-up is essential after the open-heart surgery and it can be measured in different ways, as in our case. (c) 2014 Baishideng Publishing Group Inc. All rights reserved

Modified Tension Band Wiring Technique For Olecranon Fractures: Where And How Should The K-Wires Be Inserted To Avoid Articular Penetration?

Objective: Articular penetration of K-wires is a possible complication of the modified tension band wiring technique. However, there is no clear information or evidence regarding the entry point or introduction angle for K-wires to avoid this complication. The aim of this experimental study was to evaluate the effect of varying K-wire insertion points and angles on the risk for articular penetration during modified tension band wiring for olecranon fractures. Methods: All anatomical measurements were made on 50 cadaveric ulnas, and all other measurements were performed on exact foam replications of the 50 cadaveric ulnas. Morphometric measurements, including olecranon height and heights of the central, radial and ulnar facets of the semilunar notch, were taken. In the sagittal plane, articular angle and tubercle angle were measured. Two 1.6-mm parallel K-wires were inserted from 0, 5 and 8 mm anterior to the dorsal cortex of the olecranon process at angles of 20 degrees and 30 degrees K-wire articular penetration was evaluated both visually and radiographically. Results: The mean central, radial and ulnar heights of the semilunar notch were 17.3 mm (14.7-20.0), 16.2 mm (12.0-21.0) and 15.8 mm (13.30-20.5), respectively. We observed no articular penetration at the 0-mm level at 20 degrees and 30 degrees (0 mm 20 degrees and 0 mm 30 degrees, respectively) or at 5 mm 20 degrees. At 8 mm 30 degrees wire introduction, more than 64% articular penetration was observed on either facet. The sequence from least to most likely to cause articular penetration was: 0 mm = 5 mm 20 degrees > 5 mm 30 degrees = 8 mm 20 inverted perpendicular > 8 mm 30 degrees. The radial height of the semilunar notch was negatively correlated to the risk of articular penetration, when the wire was introduced at 8 mm 30 degrees, 8 mm 20 degrees and 5 mm 30 degrees (all p <0.047). There were poor correlations between radiological and direct observational assessments, particularly for 8 mm 20 degrees and 5 mm 30 degrees. The frequency of intra-articular positioning for those observed to be radiologically extra-articular was 4/28 (14.3%) for 8 mm 30 degrees, 4/7 (57.1%) for 8 mm 20 degrees and 5/6 (83.3%) for 5 mm 30 degrees. Conclusion: When applying the modified tension band wiring technique to prevent articular penetration, K-wires should be inserted in the first 5 mm from dorsal cortex of the olecranon process at a maximum angle of 20 degrees. Moreover, if the wires are required to be inserted more anteriorly because of the anatomical configuration of the fracture, they should be inserted at a shallow angle in the sagittal plane in relation to the proximal cortex of the ulna.WoSScopu

L-myc polymorphism in head and neck nonmelanoma skin and lower lip cancers

Objective: To evaluate the presence of L-myc gene variations as a genetic predisposition to head and neck nonmelanoma skin cancer (HNNMSC) and lower lip cancer (LLC)