Preconditioning complex symmetric linear systems

A new polynomial preconditioner for symmetric complex linear systems based on Hermitian and skew-Hermitian splitting (HSS) for complex symmetric linear systems is herein presented. It applies to Conjugate Orthogonal Conjugate Gradient (COCG) or Conjugate Orthogonal Conjugate Residual (COCR) iterative solvers and does not require any estimation of the spectrum of the coefficient matrix. An upper bound of the condition number of the preconditioned linear system is provided. Moreover, to reduce the computational cost, an inexact variant based on incomplete Cholesky decomposition or orthogonal polynomials is proposed. Numerical results show that the present preconditioner and its inexact variant are efficient and robust solvers for this class of linear systems. A stability analysis of the method completes the description of the preconditioner.Comment: 26 pages, 4 figures, 4 table

Predicting aortic complications after endovascular aneurysm repair

Background Lifelong surveillance is standard after endovascular repair of abdominal aortic aneurysm (EVAR), but remains costly, heterogeneous and poorly calibrated. This study aimed to develop and validate a scoring system for aortic complications after EVAR, informing rationalized surveillance. Methods Patients undergoing EVAR at two centres were studied from 2004 to 2010. Preoperative morphology was quantified using three-dimensional computed tomography according to a validated protocol, by investigators blinded to outcomes. Proportional hazards modelling was used to identify factors predicting aortic complications at the first centre, and thereby derive a risk score. Sidak tests between risk quartiles dichotomized patients to low- or high-risk groups. Aortic complications were reported by Kaplan–Meier analysis and risk groups were compared by log rank test. External validation was by comparison of aortic complications between risk groups at the second centre. Results Some 761 patients, with a median age of 75 (interquartile range 70–80) years, underwent EVAR. Median follow-up was 36 (range 11–94) months. Physiological variables were not associated with aortic complications. A morphological risk score incorporating maximum aneurysm diameter (P < 0·001) and largest common iliac diameter (measured 10 mm from the internal iliac origin; P = 0·004) allocated 75 per cent of patients to a low-risk group, with excellent discrimination between 5-year rates of aortic complication in low- and high-risk groups at both centres (centre 1: 12 versus 31 per cent, P < 0·001; centre 2: 12 versus 45 per cent, P = 0·002). Conclusion The risk score uses commonly available morphological data to stratify the rate of complications after EVAR. The proposals for rationalized surveillance could provide clinical and economic benefits

CLIO: a Novel Robotic Solution for Exploration and Rescue Missions in Hostile Mountain Environments

Rescue missions in mountain environments are hardly achievable by standard legged robots - because of the high slopes - or by flying robots - because of limited payload capacity. We present a novel concept for a rope-aided climbing robot, which can negotiate up-to-vertical slopes and carry heavy payloads. The robot is attached to the mountain through a rope, and is equipped with a leg to push against the mountain and initiate jumping maneuvers. Between jumps, a hoist is used to wind/unwind the rope to move vertically and affect the lateral motion. This simple (yet effective) two-fold actuation allows the system to achieve high safety and energy efficiency. Indeed, the rope prevents the robot from falling, while compensating for most of its weight, drastically reducing the effort required by the leg actuator. We also present an optimal control strategy to generate point-to-point trajectories overcoming an obstacle. We achieve fast computation time ($<$1 s) thanks to the use of a custom simplified robot model. We validated the generated optimal movements in Gazebo simulations with a complete robot model, showing the effectiveness of the proposed approach, and confirming the interest of our concept. Finally, we performed a reachability analysis showing that the region of achievable targets is strongly affected by the friction properties of the foot-wall contact.Comment: 6 page

Distal Ulcerative Colitis Refractory to Rectal Mesalamine: Role of Transdermal Nicotine versus Oral Mesalamine

BACKGROUND: Distal ulcerative colitis usually responds to treatment with rectal mesalamine, but the management of refractory cases is poorly defined

Racial differences in patient-reported outcomes among men treated with radical prostatectomy for prostate cancer

Background: Real-world data on racial differences in the side effects of radical prostatectomy on quality of life (QoL) are lacking. We aimed to evaluate differences in patient-reported outcome measure (PROM) among non-Hispanic Black (NHB) and non-Hispanic White (NHW) men using the Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP) questionnaire to measure health-related QoL after radical prostatectomy. // Methods: We retrospectively assessed prospectively collected PROMs using EPIC-CP scores at a tertiary care center between 2015 and 2021 for men with prostate cancer undergoing radical prostatectomy. The primary endpoint was the overall QoL score for NHB and NHW men, with a total score of 60 and higher scores indicating worse QoL. An imputed mixed linear regression model was used to examine the effect of covariates on the change in overall QoL score following surgery. A pairwise comparison was used to estimate the mean QoL scores before surgery as well as up to 24 months after surgery. // Results: Our cohort consisted of 2229 men who answered at least one EPIC-CP questionnaire before or after surgery, of which 110 (4.94%) were NHB and 2119 (95.07%) were NHW men. The QoL scores differed for NHB and NHW at baseline (2.34, 95% confidence interval [CI] 0.36–4.31, p = 0.02), 3 months (4.36, 95% CI 2.29–6.42, p < 0.01), 6 months (3.26, 95% CI 1.10–5.43, p < 0.01), and 12 months after surgery (2.48, 95% CI 0.19–4.77, p = 0.03) with NHB having worse scores. There was no difference in QoL between NHB and NHW men 24 months after surgery. // Conclusions: A significant difference in QoL between NHB and NHW men was reported before surgery, 3, 6, and 12 months after surgery, with NHB having worse QoL scores. However, there was no long-term difference in reported QoL. Our findings inform strategies that can be implemented to mitigate racial differences in short-term outcomes

Anti-Mullerian Hormone-to-Testosterone Ratio is Predictive of Positive Sperm Retrieval in Men with Idiopathic Non-Obstructive Azoospermia

The lack of clinically-reliable biomarkers makes impossible to predict sperm retrieval outcomes at testicular sperm extraction (TESE) in men with non-obstructive azoospermia (NOA), resulting in up to 50% of unnecessary surgical interventions. Clinical data, hormonal profile and histological classification of testis parenchyma from 47 white-Caucasian idiopathic NOA (iNOA) men submitted to microdissection TESE (microTESE) were analyzed. Logistic regression analyses tested potential clinical predictors of positive sperm retrieval. The predictive accuracy of all variables was evaluated using the receiver operating characteristic-derived area under the curve, and the clinical net benefit estimated by a decision-curve analysis (DCA). Overall, 23 (49%) and 24 (51%) patients were classified as positive and negative sperm retrievals at microTESE. While circulating hormones associated to a condition of primary hypogonadism did not predict sperm retrieval, levels of anti-Mullerian hormone (AMH) and the ratio AMH-to-total Testosterone (AMH/tT) achieved independent predictor status for sperm retrieval at microTESE, with a predictive accuracy of 93% and 95%. Using cutoff values of &lt;4.62 ng/ml for AMH and &lt;1.02 for AMH/tT, positive sperm retrieval was predicted in all individuals, with 19 men out of 47 potentially spared from surgery. DCA findings demonstrated clinical net benefit using AMH and AMH/tT for patient selection at microTESE

Promoting the use of the PI-QUAL score for prostate MRI quality: results from the ESOR Nicholas Gourtsoyiannis teaching fellowship

OBJECTIVES: The Prostate Imaging Quality (PI-QUAL) score is a new metric to evaluate the diagnostic quality of multiparametric magnetic resonance imaging (MRI) of the prostate. This study assesses the impact of an intervention, namely a prostate MRI quality training lecture, on the participant's ability to apply PI-QUAL. METHODS: Sixteen participants (radiologists, urologists, physicists, and computer scientists) of varying experience in reviewing diagnostic prostate MRI all assessed the image quality of ten examinations from different vendors and machines. Then, they attended a dedicated lecture followed by a hands-on workshop on MRI quality assessment using the PI-QUAL score. Five scans assessed by the participants were evaluated in the workshop using the PI-QUAL score for teaching purposes. After the course, the same participants evaluated the image quality of a new set of ten scans applying the PI-QUAL score. Results were assessed using receiver operating characteristic analysis. The reference standard was the PI-QUAL score assessed by one of the developers of PI-QUAL. RESULTS: There was a significant improvement in average area under the curve for the evaluation of image quality from baseline (0.59 [95 % confidence intervals: 0.50-0.66]) to post-teaching (0.96 [0.92-0.98]), an improvement of 0.37 [0.21-0.41] (p < 0.001). CONCLUSIONS: A teaching course (dedicated lecture + hands-on workshop) on PI-QUAL significantly improved the application of this scoring system to assess the quality of prostate MRI examinations. KEY POINTS: • A significant improvement in the application of PI-QUAL for the assessment of prostate MR image quality was observed after an educational intervention. • Appropriate training on image quality can be delivered to those involved in the acquisition and interpretation of prostate MRI. • Further investigation will be needed to understand the impact on improving the acquisition of high-quality diagnostic prostate MR examinations

Clinical strategies for the management of intestinal obstruction and pseudo-obstruction

BACKGROUND In: Testinal obstructions/pseudo-obstruction of the smalUlarge bowel are jequent conditions but their management could be challenging. Moreover, a general agreement in this field is currently lacking, thus SICUT Society designed a consensus study aimed to define their optimal workout. METHODST:h e Delphi methodology was used to reach consensus among 47 Italian surgical experts in two study rounds. Consensus was defined as an agreement of 75.0% or greater. Four main topic areas included nosology, diagnosis, management and treatment. RESULTS: A bowel obstruction was defined as an obstacle to the progression of intestinal contents and flzrids generally beginning with a sudden onset. The panel identiJed four major criteria of diagnosis including absence of flatus, presence of > 3.5 cm ileal levels or > G cm colon dilatation and abdominal distension. Panel also recommended a surgical admission, a multidisciplinary approach, and a gastrografin swallow for patients presenting occlusions. Criteria for immediate surgery included: presence of strangulated hernia, a > 10 cm cecal dilatation, signs of vascular pedicles obstructions and persistence of metabolic acidosis. Moreover, rules for non-operative management (to be conducted for maximum 72 hours) included a naso-gastric drainage placement and clinical and laboratory controls each 12 hours. Non-operative treatment should be suspended if any suspects of intra-abdominal complications, high level of lactates, leukocytosis (> 18. 000/mm3 or Neutrophils > 85%) or a doubling of creatinine level comparing admission. Conversely, consensus was not reached regarding the exact timing of CT scan and the appropriateness of colonic stenting. CONCLUSIOTNhSis: consensus is in line with current international strategies and guidelines, and it could be a usefil tool in the safe basic ahily management of these common and peculiar diseases